mr ^.T.^.^ HATHIRDM.METCALF, If-'/ /^-A^Lj ÄATSIKDM, METCiLI, <~": ANATOMY OF THE INVERTEBRATA C. TH. V. SIEBOLD, Translated from the German with Additions and Notes WALDO I. BURNETT, M.D. x= or 2; ■ LD : r^ |o BOSTON: JAMES CAMPBELL, 18 TREMONT STREET. 1874. Entered according to Act of Congress, in the year 1S54, by GOULD & LINCOLN, In the Clerk's Office of the District Court for the District of Massachusetts. Entered according to Act of Congress, in the year 1871, by JAMES CAMPBELL, In the Office of the Librarian of Congress at Washington. PRINTED BT E. FARVVELL & CO., 34 Merchants Row, BOSTON. ^VJn\.?r)V(. XT*- Co MT ESTEEMID FRIEND, LOUIS AGASSI Z, PBOTESSOR OF ZOOLOGY, 4o., IK f arbarb tffniiersitg, WHOSE WELI.KNOWN EELATI0N3 TO COMPAKATIVE AKATOMT BEQTJUUI BO MENTIOM HKEE. AND WHOSE SPLENDID GENIUS HAS DONE 80 MUCH TO AWA« IN THIS COUNTKT ESPECIALLT, A LIVELY INTEKE3T IN OBJECTS OF NATURAL HI3T0KT, I Inscribe i\h ^almt, WITH ADMIRATION AND SINCERE GRATITÜD1. WALDO I. BURNETT. PUBLISHER'S NOTICE. For some years there has been a constant and increasing demand for a thorough and reliable text-book on the Anatomy of the Invertebrata ; and no other book having appeared upon the subject to meet the requirements and to supersede Dr. Burnett's translation of Von Siebold's Lerhbuck der vergleichenden Anatomie^ which, to- gether with the translator's valuable and extensive notes, is believed to be incomparably the best and most complete treatise on the science, and the same having been highly commended by Professors Agassiz, Silliman, Hitchcock and others, the publisher feels him- self justified in offering this edition to the student, confident that it will supply a want not at present met by any other work in our lan- guage. Boston, May, 1874. iOTÜClPTI If yjrj^. NOTICE OF THE TRANSLATOR AND EDITOR. In issuing an English translation of the Lehrbuch der rer- gleichenden Anatomie of Von Siebold and Stannius, any formal account of the work is quite unnecessary. To all Anato- mists it is a treatise already well and favorably known, and it has justly been regarded as the most complete and comprehensive work of its kind now extant in any language. The high position and distinguished reputation of its authors have been fully sustained by this portion of their labors. But there are several features in this work which should be men- tioned, since by them it is favorably distinguished from all other treatises of the kind that have preceded it. In the text will be found a lucid yet succinct exposition of thfl anatomical structure of organs, arranged as far as practicable undei? distinct types. The details on which this typical summary is based, are comprised in notes which are as remarkable for their erudition as for their copiousness ; indeed, the utmost care has been taken in the literature of the various subjects treated, and the student will here find the most reliable and nt the same time the fullest refer- ence to the bibliography of nearly every subject in Comparative Anatomy. In this way, the work as a whole furnishes a complete dictionary of the science, and will prove invaluable even as a work of suggestion and reference, to those who would pursue any special line of inquiry and research in this department. It may be truly said that the Microscope lies at the foundation of all our best knowledge of anatomy, and especially that of the Inverte- brata. This is the case, not only on account of the small size of most of the animals, but because, as Von Siebold has said in his preface, the anatomy of these lower forms is scarcely reliable unless based upon histological investigations. VIII NOTICE OF THE TRANSLATOR AND EDITOR. Hence, that part of the work treating of the anatomy of the Invertebrata, by Von Siebold, is rich in the results of microscopi- cal researches ; and their value in the elucidation of the subject ■will be readilj appreciated. This plan of procedure has not the same urgency vrith the higher animals, -where the character of an orofan or part can generally be ascertained from its position, &C. ; and, in the second part of the work, on the Anatomy of the Vertebrata, by Stannius, details of microscopical structure are comparatively little insisted upon. But, within a few years, the histological compo- sition of organs, even though their character and function is well known, has become of great and increasing interest ; and details of this kind, as far as they would be understood without the aid of figures, I have sought to add in their regular order and place. As to the notes and additions generally, they stand by themselves with Ed. affixed, and almost invariably refer to some point treated of in the text or notes of the original, and for the most part relate to the correction, confirmation, or extension of some statements there made. These notes were drawn from all the sources accessible to me; but from the many difficulties in the way of the early receipt of foreign works in this country, they are not as complete a record of the recent progress of the science as would be desired. As to the translation, I may say, that not being a German scholar, but having read the German language chiefly for scientific purposes, I trust that any inelegances of diction or idiom will be excused. But, throughout, I have endeavored to give a faithful rendering of the author's meaning, and to express this in as simple and terse a form as possible. In conclusion, I wish to express my gratitude to my friends who have kindly aided me in this work ; — prominent among these is Mr. Edward Capen of this city, who has been of invaluable assistance to me in the labor of passing the sheets of this volume through the press ; — of others, such as Professors Agassiz, Dana, Leidy, and Wyman, their names will be found honorably recorded by their own important labors in science, to Avhich I have so frequently referred in these volumes. W. I. B. Boston, Nov. 1853. PREFACE. As latterly, Zootomists have given much greater attention to the invertebrate animals than formerly ; and as, with these investigations they have united, as much as possible, others upon the generation and development of these animals, such a mass of material, composed, in part, of entirely new and very remarkable facts, has accumulated, that the manuals of Zootomy hitherto published are of a scale quite inadequate to receive them. It is unnecessary, therefore, for me to ■offer further reason for the task I have undertaken of arranging these materials and reducing them to a systematic form. But the order in which I have disposed them may not meet with general approval, for, hitherto, in works of comparative anatomy, the organs, and not the zoological classes, have served as the basis of the order pursued. But, in the present state of Science, and at least provisionally, it appears to me that the anatomical order should not be followed, for, the types, which, until now, have been recognized in the develop- mental series of the several organs, appear no longer valid and permanent. Indeed, extended researches made upon a great number of animals, have shown that these types, hitherto regarded as express- ive of fundamental laws, may almost be taken as the exceptions. Such genera as Hydra, Lumbricus, Hirudo, Unio, Astacus, &v. , can now no longer be regarded as the representatives of certain animal classes or orders, for their organization is far from affording the requisite type of that of allied animals. It appears now clearly determined that the types of the development and disposition of the various organs of the Invertebrata are more numerous and varied than hitherto supposed, and that, in this respect, a rule wholly differ- ent from that of those of the Vertebrata must here be applied. But as the numberless details which we now possess upon the organization of the Invertebrata, have not been thoroughly worked out and system- atized in all the orders, it is really a task too difficult to here distinguish the rule from the exception, and the type from that which. is only a secondary modification. X PREFACE. I have especially devoted myself to the collecting and collating as completely as practicable, the numerous new and important facts in the organization of the invertebrate animals, which have as yet been developed. And as occasion presented, I have verified with my own eyes the particular results ; and when I have been obliged to refer to the discoveries and observations of others, I have cited exactly their works. I could not exclude Embryology and Histology from this work, for, in these branches, often lies our only means not only to ascertain the true nature of many larval forms among the lower animals, but also to arrive at the correct interpretation of many organs which, in form, position, and arrangements, have no analogues among the higher animal forms. It is only by the aid of Histology that we aie able to show that this or that organ is a branchia, a liver, a kidney, an ovary, or a testicle ; while, in the Vertebrata, which are organized after a few principal types, the signification of most of the organs can usually be easily determined by their position and connection. In order to avoid long descriptions, I have, when practicable, re- ferred to plates and figures ; but in so doing I have always endeavored to cite the good and original representations, for I am convinced that many figures which are transferred from one book to another, become, at last, so changed as to be quite dissimilar to the original. The elaboration of this work having been commenced in 1845, but its completion having been delayed by my change of residence from Erlangen to Freiburg, and partly by a pretty long sojourn of mine on the Adiiatic Sea, I have been unable to use the important works which have been published during the last few years, except in the form of a Supplement [additional notes] which will serve to com- plete, to confirm, or to rectify what has been advanced in the body of the work. I take this opportunity to publicly express my gratitude to A. Kölliker, H. Koch, A. Krohn, C. Vogt, and H. Stannius, for the friendly and important aid they have rendered me in the completion of this difficult task — not only by the transmission to me of inter- esting and rare marine animals, but also in the communication of important manuscripts and letters, the contents of which they have allowed me to freely use for my work. Feeiburg (in Breisgau), Feb. 27, 1848. C. Th. v. SIEBOLD. JÄAISülD M, METOaL^ TABLE OF CONTENTS. ■BCTIOH Claseification of the Invertebrate Animals, 1 Bibliography, « 2 Introductory JVbte to the Infusoria. I. THE INFUSORIA AND RHIZOPODA. Classification and Bibliography, . 3-5 1. External Covering 6 2. Muscular System, and Locomotive Organs, 7-8 3, 4. Nervous System, and Organs of Sense, 9-10 5. Digestive Apparatus, 11-15 6, 7. Circulatory and Respiratory Systems, 16-18 8. Organs of Secretion, 19 9. Organs of Beproduction, 20-23 Introductory JVbte to the Zoophyta. n. THE POLYPI. Classification and Bibliography, 24 1. Cutaneous Envelope and Skeleton, 25-2S 2. Muscular System, and Organs of Locomotion, 29-32 8, 4. Nervous System, and Organs of Sense, 33-34 5. Digestive Apparatus, 35-36 Digestive Cavity of the Anthozoa, 37 Digestive Cavity of the Bryozoa, 3B 6, 7. Circulatory and Respiratory Systems 39-41 8. Organs of Secretion 42 9. Organs of Generation, 43-52 m. THE ACALEPHAE. Classification and Bibliography • 53 1. Skin and Cutaneous Skeleton 54-56 2. Muscular System, and Organs of Locomotion, 57-58 3. Nervous System 59 4. Organs of Sense, 60 5. Digestive Apparatus, 61 6. Circulatory System, 62 7. Respiratory System, 63-64 39744 XII CONTENTS. SECTIO!» 8. Organs of Secretion, 65 9. Organs of Generation, 66-70 IV. THE ECHINODERMATA Classification and Bibliography, 71 1. Cutaneous Envelope and Skeleton, 72-75 2. Muscular System, and Organs of Locomotionj 76-78 8. Nervous System 79-80 4. Organs of Sense, 81 5. Digestive Apparatus, 82-86 6. Circulatory System, 87-88 7. Respiratory System 89-93 8. Organs of Secretion, 94 9. Organs of Generation, ^ . . 95-98 V. THE HELMINTHES. Classification and Bibliography, 99 1. Cutaneous System, 100-101 2. Muscular System, and Organs of Locomotion 102-103 3. Nervous System 104 4. Organs of Sense 105 5. Digestive Apparatus, » 106-109 6. Circulatory System 110-111 7. Respiratory System, 112 8. Organs of Secretion, 113 9. Organs of Generation, 114-119 VI. THE TURBELLARIA. Classification and Bibliography 120 1. Cutaneous System, 121 2. Muscular System, and Locomotive Organs, 122 3, 4. Nervous System, and Organs of Sense, 123-124 5. Digestive Apparatus 125 6, 7. Circulatory and Respiratory Systems, 126 8. Organs of Secretion, 127 9. Organs of Generation, 128-129 VII. THE ROTATORIA. Classification and Bibliography, 130 1. Cutaneous System, 131 2. Muscular System, and Locomotive Organs, 132-133 3, 4. Nervous System, and Organs of Sense, 134-135 6. Digestive Apparatus, 186 6, 7. Circulatory and Respiratory Systems 137-138 8. Organs of Secretion, 139 9. Organs of Generation, 140-141 VIH. THE ANNELIDES. Classification and Bibliography, 142 1. Cutaneous System 143 2. Muscular System, and Locomotive Organs, 144-145 CONTENTS. Xin SECTION 3. Nervous System 146-148 4 Organs of Sense, 149-151 I. Organs of Touch, 14'.) II. Organs of Vision 150 III. Organs of Hearing, • 151 6. Digestive Apparatus, 152-155 I. Organs of Deglutition and Mastication 158 II. Intestinal Canal, 154 III. Glandular Appendages, 155 6. Circulatory System, 156-157 7. Respiratory System, 158-160 8. Organs of Secretion, 161 9. Organs of Generation, 162-169 IX. THE ACEPHALA. Classification and Bibliography, 1 70" 1. Cutaneous System, 171-175 2. Muscular System, and Organs of Locomotion, 176-180 3. Nervous System, 181-184 4. Organs of Sense, 185-187 5. Digestive Apparatus, 188-190 6 Circulatory System, 191-192 7. Respiratory System 193-195' 8. Organs of Secretion, . • 196 9. Organs of Generation 197-200 X. THE CEPHALOPHORA. Classification and Bibliography 201 1. Cutaneous System 202-203 2. Muscular System, and Organs of Locomotion, 204-205 3. Nervous System, 206-209 4. Organs of Sense, 210-212 5. Digestive Apparatus, 213-215 6. Circulatory System, 216-218 7. Respiratory System, 219-222 I. Branchiae, 220 II. Lungs, 221 III. Aquiferous System, • 222 8. Organs of Secretion, 223-224 I. Urinary Organs, 223 n. Organs of Peculiar Secretions, 224 9. Organs of Generation, 225-229 XI. THE CEPHALOPHODA. Classification and Bibliography, . 230 1. Internal Skeleton, 231-282 2. Cutaneous Envelope, 233-235 3. Muscular System, and Organs of Locomotion, 236-238 4. Nervous System, 239-242 5. Organs of Sense, 243-247 6. Digestive Apparatus, 248-250 7. Circulatory System, 251-552 8. Respiratory Organs, 253-254 2 XIV CONTENTS. BICTtO* 9. Organs of Secretion 255-266 L Urinary Organs, 255 n. Organs of Special Secretions, 256 10. Organs of Generation, 257-261 Introductory JVote to the Crustacea. XH. THE CRUSTACEA. Classification and Bibliography, 262 1. External Envelope, and Cutaneous Skeleton 263-266 2. Muscular System, and Organs of Locomotion, 267-269 a Nervous System, 270-273 4. Organs of Sense, 274-277 6. Digestive Apparatus, 278-281 6. Circulatory System, 282-284 7. Respiratory System 285-287 g. Organs of Secretion, 288-289 J. urinary Organs 288 11. Organs of Special Secretions, 289 :9. Organs of Generation, 290-294 I. ilermaphrodite Crustacea, 291 II. Female Crustacea, 292 III. Male Crustacea, 293 Xlir. THE ARACHNOIDAE. Classification and Bibliography, 295 1. External Envelope, and Cutaneous Skeleton, 296-397 ■2. Muscular System, and Org.ans of Locomotion, 298-299 3. Nervous System, 300-302 4. Organs of Sense, 303-305 Ö. Digestive Apparatus, 306-308 6. Circulatory System 309-310 7. Respiratory System, 311-313 8. Organs of Secretion, 314-315 I. Urinary Orgms, 311 II. Oi'g.uis of S|iecial Secretions, 315 9. Organs of Generation, 316-320 I. Hermaphrodite Arachnoidae, 317 II. Female Arachnoidae 318 III. M.ile Arachnoidae, 319 XIV. THE INSECTA. Classification and Bibliography, 321 1. External I'nvelope, and Cutaneous Skeleton, 322-323 2, Muscular System, and Locomotive and Soniferous Organs, 325-327 8. Nervous System 328-331 4. Organs of Sense 332-336 5. Digestive Apparatus, 337-339 6. Circulatory System, 340 7. Respiratory System, 341-344 8. Organs of Secretion, 345-347 I. Urinary Organs, 345-346 II. Organs of Special Secretions, 347 9. Organs of Generation, 348-355 I. Female Genital Organs, 349-351 II. Male Genital Organs, 352-354 Index ^C4>s.^ '<:$^ao^^ ^< CLASSIFICATION or THE INVERTEBRATE ANIMALS. §1- The invertebrate animals are organized after various types, the limits of which are not always clearly defined. There is, therefore, a greater number of classes among them than among the vertebrates. But, as the details of their organization are yet but imperfectly known, they have not been satisfactorily classified in a natural manner. There are among them many intermediate forms, which make it difficult to decide upon the exact limits of various groups. The following division, however, from the lowest to the highest forms of organization, appears at present the best : ANIMALIA EVERTEBRATA. INVERTEBRATE ANIMALS. Brain, spinal cord, and vertebral column, absent. FIRST GROUP. PROTOZOA. Animals in which the different systems of organs are not distinctly sep- arated, and whose irregular form and simple organization is reducible to the type of a cell. Class I. Infusoria. Class II. Rhizopoda. SECOND GROUP. ZOOPHYTA. Animals of regular form, and whose organs are arranged in a ray-like manner around a centre, or a longitudinal axis ; the central masses of the nervous system forming a ring, which encircles the oesophagus. Class III. Polypi. Class IV. Acalephä. Class V. Echinodkrmata, 16 CLASSIFICATION. <^2. THIRD GROUP. VERMES. Animals with an elongated, symmetrical body, and whose organs are arranged along a longitudinal axis; so that right and left, dorsal and ventral aspects may be indicated. The central nervous mass consists of a cervical' ganglion, with or with- out a chain of abdominal ganglia. Class VI. Helminthes. Class VII. Turbellarii. Class VIII. Rotatorii. Class IX. Annulati. FOURTH GROUP. MOLLUSCA. Animals of a varied form, and whose bodies are surrounded by a fleshy mantle. The central nervous masses consist of ganglia, some of which surround the oesophagus, and others, connected by nervous filaments, are scattered through the body. Class X. Acephala. Class XI. Cephalophora. Class XII. Cephalopoda. FIFTH GROUP. ARTHROPODA. Animals having a perfectly symmetrical form, and articulated organs of locomotion. The central masses of the nervous system consist of a ring of ganglia surrounding the oesophagus, from which proceeds a chain of abdominal ganglia. Class XIII. Crustacea. Class XIV. Arachnida. Class XV. Insecta. BIBLIOGRAPHY, §2. Besides the various ancient and modern works upon general comparative anatomy, — such as those of Blumenbach, ^^'' G. Cumer,^-' F. Meckel,^^^ E. Home,^*' Blai?iville,^'^' Delle ChiaJe/'^Carus,'^'Grant,'^^^Ry7ner Jones, '^^^Straitss 1 Hamltmch der vergleichenden Anatomie. Göt- tinpen, 18vM. ü I/;(,-oiii) (i'Anatomie comparee. Paris, 1799- 1805. Trantiliit<'d into German and iiutilished with note» and additions Ijy Meckel and Froriep. i vols. I/eipr.iK, 1809-10. 2nd edit. Paris, 18155-^5. 3 System der vergleichenden Anatomie. 6 vols. Halle, 1821-33. * Lectures on Comparative Anatomy. 6 vols. JiODdoD. 1814-29. ' De I'Orpanisation des Animaux, ou Principe» d'Anatomie compar*e. Tom. I. Paris, 1832. ^ Istituzioni di Anotomiae Kisiologia Comparata. Napoli, 1832. 7 Lehrbuch der vergleichenden Anatomic. 2nd ed. Leipzig, 1834. " Outlines of Comparative Anatomy. Ixindon, 1841. I' A General Outline of the Animal Kingdom, an and in the Medical Zoology of Brandt and Ratzebiirg}^^^ The iconographic illustrations by Cams and Otto,^'^^ and by R. Wag- Tzer/-"' contain many plates representing these animals; and in G?/erm's Iconographie,^-^^ and Conner' s ^''■'-'' Regne Animal, edited by several French naturalists, are many illustrations of their internal structure. The following are some of the anatomical works which treat specially upon these animals : Schweigger. — Handbuch der Naturgeschichte der skelettlosen unge- gliederten Thiere. Leipzig, 1820. Delle Chiaje. — Memorie su la Storia e Notomia degli Animali senza Vertebra del regno di Napoli. 4 vol. Napoli, 1823-29. 109 tavole. A second and enlarged edition of this memoir has been published under the following title : Descrizione e notomia degli animali invertebrati della Sicilia citeriore. 1-5, vol. Napoli, 1841. Con tavol. I.-CLXXIL Sars. — Beskrivelser og Jagttagelser over nogle moerkelige eller nye i Havet ved den Bergenske Kyst levende Dyr af Polypernes, Acalephernes, Radiaternes, Annelidernes og Molluskernes Classer. Bergen, 1835. Lamarck. — Histoire Naturelle des Animaux sans Vertebres. Deux, edit., par Deshayes et Milne Edwards. 11 vols. Paris, 1835-45. Mibie Edivards. — Elemens de Zoologie, ou Lecons sur I'Anatomie, la Physiologie, la Classification, et les Moeurs des Animaux. Deux. edit.. Animaux sans Vertebres. Paris, 1843. Richard Owen. — Lectures on the Comparative Anatomy and Physiology of the Invertebrate Animals. London, 1843. H. Frey and R. Leuckart. — Beiträge zur Kenntniss wirbelloser Thiere mit besonderer Berücksichtigung der Fauna des norddeutschen Meeres. Braunschweig, 1847. These same naturalists have prepared the second part of Wagner's Lehrbuch der Zootomie, under the special title of: Lehrbuch der Anatomia der wirbellosen Thiere. Leipzig, 1847. Stef. Andr. Renier. — Osservazioni postume di Zoologia adviatica pub- blicate per cura dell' istituto veneto di scienze, lettere ed arti a studio del Prof. G. Meiieghini. Venezia, 1847. Con tavol. I.-XVL 1" Trait* pratique et thioretique d'Anatomie eomparie. 2 vol. Paris, 1842. 11 Lehrbuch der Zootomie. 2nd edit., entirely re- vised ; or " Lehrbuch der vergleichenden Anato- mie." Leipzig, 1842. 12 Biologie. 6 vol. Göttingen, 1802-22. Also ; Erscheinungen und Gesetze des organischen Le- bens. 2 vol. Bremen, 1831-33. 1^ Grundriss der Physiologie. 2 vol. Berlin, 1821-28. 1^ Trait§ de Physiologie comparee de l'IIomrae et des Animaux. 3 vol. Montpellier, 1838-39. IS Die Physiologie als Erfahrungswissenschaft, erste Auflage, mit Beiträgen von C. v. Baer, Dieff'enbach, J. Mn/ter, R. fVa^ner. 6 vol. Leipzig, 1826-40. 2 te Auflage, mit Beiträgen von E. Meyer, II. Rathki, C. v. Siebold und G. Val- entin. 2 vol. Leipzig, 1835-37. 1^ Handbuch der Physiulogie des Menschen. 2 Tol. 4th edit. Coblentz, 1844. 2^ 1' Lehrbuch der Physiologie. 2nd edit. Leipzig, 1843. 18 Medicinische Zoologie. 2 vol. Berlin, 1829-33. lä Erlfluterungstafeln zur vergleichenden Anato- mie. 6 lieft. Leipzig, 1826-43. -0 Icones physiologicae. Erläuterungstafeln zur Physiologie und Entwickelungsgesr.hichte. Leip- zig, 1839. Also, Icones Zootomicte. Handatlas zur vergleichenden Anatomie. Leipzig, 1841. 21 Iconographie du R^gne Animal de G. Cuvier, ou Representation d'apr^s natura de l'une des esp^ces les plus remarquables et souvent non en- core figurees de chaque genre d' Animaux ; pour servir d'atlas dl tous les Traites de 7x)ologie. 1 vol. avec 450 planches. Paris, 1830-38. " Regne Animal de Cuvier, nouvelle Edition, ac- compagn^e de planches gravees, &c. &c. Paris 1836-47. Still unfinished. INTRODUCTORY NOTE TO THE INFUSORIA. Constant labors ia the whole department of microscopy, and that, too, with greatly improved instruments, during the past few years, have materially changed the face of the class Infusoria since the issue of this work. There have been numerous and signal researches among all the lower forms of animallife; and the imperfect and undeveloped forms of others, which are higher, have been wrought out with an accuracy and detail before unknown. These movements have all tended to diminish the numbers of the so- called Infusoria, and it remains to be seen how large the proper class will be when these researches shall have been further extended. By some even it is believed that it will be entirely. resolved into other classes; this view however, would appear far from being warranted by our present knowl' edge; for, while, on the one hand, whole genera have been shown to be only larval worms {Bursaria, Paramcecium, &c., from Planaria ),* yet, on the other, some forms have manifested phenomena and changes lead'in«. us to place them almost unhesitatingly among individual animals. In Its best aspects, however, the subject has many perplexing points; and, in Its present unsettled state, it is almost hazardous for a scientific man to entertam anything like positive views thereon. I need scarcely allude to the vegetable, algous character which whole sec tions of the Polygastrica have recently assumed ; and the limits of this work will not allow me to discuss in detail this and other interesting points. But there are two or three topics of the highest physiological import, which are pi-onimently introduced by these studies. These are. What is a plant? What IS an animal ? and, Are the aninuU and vegetable kingdoms on their lowest confines separate and distinct from each other ? As IS well known all the older criteria by which animals were separated fron plants have long since been regarded invalid; and some of those wh,ci.„ late years have been regarded among the most constant, have, Ivn 7T'^ "^'"^ '' "^"^"^ ^"^«»"d- Cellulose has been Äolh/ceri has insisted that some forms which have neither mouth nor stom- ^ M.o,.-.. Ann. Nat. Ili.t. VL 1850. p. t K'lU.er. SUtolä and KOlUker^. Zeit.ch. I. I»i9, li. 198. INTRODUCTORY NOTE TO THE INFUSORIA. 19 ach, but consist of a homogeneous mass, are true animals. If these premises are correct, nothing will remain, as I conceive, for a distinctive characteristic, but voluntary motion. This, when positive, is indubitable evidence of any given form being of an animal character; and it must remain for each individual observer to determine what is, and what is not, voluntary action, in each particular case. Moreover, even should KOM- ker's view of a stomachless animal prove correct, the inverse condition of a true stomachal cavity being present, must, I think, be regarded as posi- tive evidence of the animal nature of the form in question; for this must always be a distinctive characteristic of the two kingdoms, when present. In regard to the other point. What constitutes an animal? observers are very far from being agreed. Siebold, KOliker, and others, have taken the ground that individual animal forms may be unicellular ; or, in other words, that an animal may be composed of only a single cell.^ This view is principally due to KcUiker's observations and statements upon Gregari- nae.t The facts are indeed striking, but the evidence does not appear to me sufficient, as yet, to settle such a vexed and important question ; and more especially so since Brückt has raised the point of their belonging to the Worms. But, aside from such grounds, I was led, some time since, after considerable study of infusoria-forms, to venlure an opinion quite at variance with that just mentioned of Siebold and Kclliker. I then made the following statement : In regard to the question, What characteristic in organic animal matter shall constitute an individual ? I feel satisfied of this much, — that cell processes, however closely interwoven they may be with the expressions of individual life, cannot be considered as constituting the ground-work of its definition. § This statement was made more than two jears since ; and subsequent observations, some of them of a special char- acter, have not led me to a change of opinion. True individual animal life seems to involve a cycle of relations not implied in simple cells; m other words, these last must always lose their character as such, in a definite form which belongs to the individual. On this account I regard the Infusoria proper, or those which have been shown to be of an undoubted animal character, as in a completely transition state; and, although it may be well to arrange these forms systematically, for the sake of convenience, yet they cannot be considered as holding fixed zoological positions. Further research in this direction, and upon " Alternation of Generation," will, I think, widely clear up this^ obscure, yet most interesting field of study. Editor. * Stebold. Siebold and KolUker's Zeitsch. t Bruch. Siebold and KmUker^^ Zeitsch. 'I'Kolliker. Siebold B.udKölUker'.ZoiUch. § Burnett. Proceed. Boston Soc. Nat. I. p. 1-. Hist. V. p. 124. BOOK FIRST. INFITSOEIA AND RHIZOPODA CLASSIFICATION. §3. The Infusoria, using this word in a restricted sense, are far from being the highly-organized animals Ehrenberg has supposed. In the first place, on account of their more complicated structure, the Rotifera must be quite separated from them, as has already been done by Wiegviann, Burmeister, R. Wagner^ Milne Edwards, Rymer Jones, and others. The same may be said of the so-called Polygastrica. In fact, a great number of the forms included under Closterina, Bacillaria, Volvocina, and others placed by Ehrenberg among the anenteric Polygastrica, belong, properly, to the vegetable kingdom. Indeed, this author has very arbitrarily taken for digestive, sexual, and nei-vous organs, the rigid vesicles, and the colored- or colorless granular masses, which are met with in simple vegetable forms,, but which are always absent in those low organisms of undoubtedly aa animal nature. Cell-structure and free motion are the only two character- istics in common of the lowest animal and vegetable forms ; and since- Schwann *^' has shown the uniformity of development and structure of animals and plants, it will not appear strange that the lowest conditions of each should resemble each other in their simple-cell nature. As ta motion, the voluntary movements of Infusoria should be distinguished from those which are involuntary, of simple vegetable forms; a distinction not insisted upon until lately. Thus, in watching carefully the motions of Vorticellina, Trachelina, Kolpodea, Oxytrichina, &c., one quickly per- ceives their voluntary character. The same is true of the power of con- tracting and expanding their bodies. But in the motions of vegetable forms other conditions are perceived* and there is no appearance of volition in either change of place or form, their locomotion being accomplished either by means of cilia, or other- physical causes not yet well understood. Cilia, therefore, belong to vegetable as well as to animal forms, and in this connection it is not a little remarkable that in animals they should be under the control of volition. With vegetable forms these organs are met with either in the shape of ciliated epithelium, as upon the spores of Vaucheria,^^^ or as long, waving filaments, as upon the earlier forms of many conferva3,<^' in which last can 1 Mikroskopische Untersuchungen, &c. Berlin, teurs des spores des Alpues. Ann. des Sc. NaL 1839 Botiin. 18«, XIX. p. 266. I'l. XI. fig. 29-30. * Tkuret. Recherches sur les organes locomo- ^ The same. I'l. X. ^§ 4, 5. INFUSORIA AND RIIIZOPODA. 21 often be seen the so-called organization of JLhrenherg's Monadina and Volvocina. Until the fact that ciliated organs belong to both animals and vegetables was decided, the real place of many low organisms had to remain undetermined/''* However, notwithstanding their free motion from place to place by means of cilia, the vegetable nature of many organisms seemed clearly indicated by the rigid, non-contractile character of their forms. It is from a misapprehension of the true nature of these facts, that some modern naturalists have denied the existence of limits between the two kingdoms. '^' With Bacillarese and Diatomaceae, this question has another aspect. Many of these organisms have been taken for animals from their so-called voluntary movements, which truly entirely want the character of volition. In the movements of the rigid Diatomacege, for instance, the whole plant has oscillatory motions like a magnetic needle, at the same time slightly changing its place forward and backward. When small floating particles come in contact with such an organism, they immediately assume the same motion. This may be well observed with the Oscillatoria, There are here, undoubtedly, no ciliary organs ; in fact, they could not, if pres- ent, produce this kind of motion. According to ^Are^i^er^,'"* the Naviculae can protrude ciliary locomotive organs through openings of their carapace; but this has not been observed by other naturalists. §4. The Rhizopoda, whose internal structure is as yet imperfectly known, are closely allied to the Infusoria. Like these last, their bodies are cellu- lar, containing nuclear corpuscles, but no system of distinct organs. These two classes of Protozoa differ, however, in their external form, and the structure of their locomotive organs. The body of the Infusoria, notwith- standing its contractility, has a definite form, and moves chiefly by means of vibratile organs. That of the Hhizopoda, on the other hand, although equally contractile, has no definite form ; their movements also are not due to ciliated organs, but to a change of the form of the body by various prolongations and digitations. §5. Owing to the present incomplete details upon the organization of these animals, little can here be said about them ; and therefore, instead of devoting to them a separate chapter, it will be proper to treat of them with the Infusoria in general. As the division of the Polygastric Infusoria, by Ehrenherg, into two < As an example, may be mentioned the various Also, Kiitzing, TJeber die Verwandlung der and dissimilar opinions of naturalists upon the Infusorien in niedere Algenformen. Nordhausen, question of the animal or vegetable nature of the 1844. "red snow;" a question upon which Flntow, In an academic paper (Dissertatio de finibus after the most careful studies, is still undecided, inter regnum animale et vegetabile constituendis. See Flotow, " Ueber Haematococcus pluvialis, " Erlangae, 1844), I have attempted to show that this in Nov. Act. Acad. Leop. Carol, vol. XX. part ii. confusion between the two kingdoms does not exist, p. 18. 6 Abhandlungen der Akademie der Wissen- 6 See Unger, Die Pflanze im Momente der Schäften zu Berlin, 1836, p. 134, Taf. I. flg. 19, and Thierwerdung. Wien. 1843. 1839, p. 102, Xaf. IV. flg. 5. 22 INFUSORIA AND KUIZOPODA. ^ i>. orders, Anentera and Enterodela, appears unfounded, the following class- ification seems more natural : PROTOZOA. Class Infusoria. Organs of locomotion chiefly vibratile, * ORDER I. ÄSTOMA. Without an oral aperture. Family: Astasiaea. Genera : AmUyophis, Euglena, Chlor ogonium Family : Peridinaea. Genera : Peridinium, Glenodinium. Family : Opalinaea. Genus : Opalina. ORDER IL STOMÄTODÄ. With a distinct oral aperture and oesophagus. Family : Vorticellina. Genera : Stentor, Trichodina, VorticeUa, Epistylis, Carchesium, Family : Ophrydina. Genera : Vaginicola, Cothurnia. Family : Encuelia. Genera : Actinophrys, Leucopkrys, Prorodon. Family: Trachelina. Genera : Glaucoma, Spirostomum, Tracheliiis, Loxodes, Chilodon, VhidliTia, Bursaria, Nassula. Family : Kolpodea. Genera : Kolpoda, ParamcBcium, Amphileptus. Family : Oxytriciiina. Genera : Oxytricha, Stylonychia, TJrostyla. Family : Euplota. Genera : Euplotes, HimantopJwriis, Chlamidodon^ ^ 5. INFUSORIA AND RHIZOPODA. 23 Class Rhizopoda. Organs of locomotion consisting of completely retractile, ramifying prolongations of the body. ORDER I. MONOSOMATIÄ. Family : Amoebaea. Genus : Amoeba. Family : Arcellina. Gonera : Arcella, Difflugia, Gromia, Miliola, Euglypha, Trinema. ORDER IL POLYSOMATIA. Genera : Vorticialis, Geoponus, Nonionina.^^ BIBLIOGRAPHY O. F. Midler. Animalcula Infusoria. Hafniae, 1786. Ehrenberg. Die Infusionsthierchen als vollkommene Organismen. Leipzig, 1838. Also his numerous and important memoirs upon the Infusoria and Rhizopoda in the- Memoirs of the Berlin Academy, and its Monthly Bulletin. Andrew Pritchard. A History of Infusoria, living and fossil, arranged according to the " Infusionsthierchen," of Ehrenberg. Illustrated by nearly 800 colored engravings of these curious creatures, highly magnified. London, 1841. Kutorga. Naturgeschichte der Infusionsthierchen, vorzüglich nach Eh- renberg's Beobachtungen bearbeitet. Calsruhe, 1841. Dujardin. Histoire Naturelle des Zoophytes. Infusoires, Paris, 1841. This work treats also of the Rhizopoda. ADDITIONAL BIBLIOGRAPHY. Besides the various articles quoted in the additional notes I have made the following are among the more important recent writings on this subject : Cohn. Beiträge zur Entwickelungsgeschichte der Infusorien, in Siebold & Kölliker's Zeitsch. III. Hft. 3, and IV. Hft. 3. Ecker. Zur Entwickelungsgeschichte der Infusorien, in Siebold & Kol' liker's Zeitsch. III. Hft. 4. Stein. Neue Beitr. zur Kenntn. d. Entwickelungsg. u. d. feineren Baues d. Infusionsthiere, in Siebold & iCöKiA-er's Zeitsch. III. p. 475, Pritchard. A History of Infusorial Animalcules, living and fossil, &c., with illustrations, new edition. London, 1852. See also numerous notes in the Annales des Sciences Naturelles, since 1847. — Ed. 1 In this table are mentioned the families and genera of those only which have Veen the objects of anatomical study. «24 • INFUSORIA AND RHIZOPODA. >§>§ 6, 7, 8. CHAPTER I. EXTERNAL COVERING. §6- The Protozoa are surrounded by a very delicate cutaneous envelope, which is sometimes smootii/^' and sometimes covered with thickly-set cilia.® Generally these cilia are arranged in longitudinal rows ; *^_' but in Actino- phrys they consist of long contractile filaments of a special nature. CHAPTER II. MUSCULAR SYSTEM AND LOCOMOTIVE ORGANS. With the Protozoa a distinct muscular tissue cannot be made out, but the gelatinous substance of their body is throughout contractile. It is only in the contractile peduncle of certain Vorticellina, that there can be perceived a distinct longitudinal muscle, which, assuming a spiral form, can contract suddenly like a spring. ^^* The Vibratile Organs on the surface of Infusoria serve as organs of locomotion. With many species they are found much developed at certain points, and are arranged in a remarkable order and manner. With Peridinium, a crown of them encircles the body; with Stylony- chia, they are quite long, and surround the flattened body like a fringe ; while the Vorticellina have the anterior portion of their body surrounded "by retractile cilia, arranged in a circular or spiral manner. In Trichodina there is, upon the ventral surface, besides a crown of these cilia upon the back, a very delicate ciliated membranous border, which is attached to a ring which is dentated, and composed of a compact homogeneous tissue. With Trichodina pediculus this border is whole and entire; but it is "broken or ragged with Trichodina rnitra.'^^ By means of this organ these animals swim with facility, or invade with skill the arm-polyps and Planaria.*-* With many Infusoria, the vibratile organs are situated at the anterior extremity of the body, as simple or •double non-retractile filaments, which move in a manner to produce a vor- > Euglena, Amoeba, (fC. i This Infusorium was discovered by me as a 2 Traclielius, Pararntecium. Nassula^ffC. parasite in many Planarieae. 3 Amphileptus, C/iilodon, Opfilina, ifC. * Ehrenbcrs: has entirely overlooked the ciliated 1 The peduncle is simple with yorticella, but border of 7VieAo(/ina ;yeu7eu/UÄ, and has regarded ramified with Carchesiam. With Epistylis it is the stiff serrations of the ring as movable hooks, not muscular. See " Die Infusionslhierchen," p. 206. §>§ 9, 10. INFUSORIA AND RHIZOPODA. 25 tical action of the water. '■^' But with others the locomotive organ is a long retractile proboscis.'^' With the Oxytrichina and Euplota, there are üßshy movable points (üncini) upon the ventral surface, by which these animals move about as upon feet. During these movements with the Oxy- trichina, the posterior portion of the body is supported by many setose and styloid processes, which point backward. The singularly varied and branching locomotive organs of the Rhizo- poda are short, and digitated with A?ncBba, Difflugia and Arcella.^^^ But in the other genera they are elongated and filamentous/*'' CHAPTERS III. AND IV. NERVOUS SYSTEM AND ORGANS OF SENSE. §9. Although the Infusoria clearly evince in their actions the existence of isensation and volition, and appear susceptible of sensitive impressions, yet no nervous tissue whatever has as yet been found in them. If Ehreii- berg supposed the Polygastric Infusoria to possess a nervous system, he did so because, having decided that the red pigment points of these ani- mals were eyes, he inferred that they necessarily had a nervous ganglion ^t their base. §10. With the naked Infusoria the sense of touch exists, undoubtedly, over the whole body. But beside this, it appears specially developed, in many species, in the long cilia forming vibratile circles, or in those movable foot-like and snout-like prolongations of the body. In the same manner, it is probable they have the sense of taste also ; for they seem to exercise a choice in their food, although no gustatory organ has yet been found. All species, whether they have red pigment points or not, seem affected by light. Without doubt, therefore, their vision consists simply in discrimi- nating light from darkness, which is accomplished by the general surface of the body, and without the aid of a special optical organ. The simple pigment point of many Infusoria,'^' and which ^Äre/iZ^erg' has generally regarded as an eye,*^' has no cornea, and contains no body capa- ble of refracting light ; there is, moreover, connected with it no nervous substance. Ehrenberg attaches here too great an importance to the red color of the 8 Amblynphis, Euglftia and Peridinium, have Sc. Nat. Zool. IV. 1S36, p. 343, pi. IX. ; also, V. A simple tlagellifoim cilium, but with Chlorogo- 1836, p. 196, pi. IX. fig. A. See, also, his Jlistoire nium it is double. des Infusoires, 1S41, p. 249. pi. I. fig. 14-17 ; pi. * Tracke/ius trichophorus feels about with a II. fig. 1, 2, 7 — 10 ; pi. IV. fig. 1); Geoponus Stel- lung snout of this kind, without, however, produc- la borealis, Nonionina germatiica, according to ing a vortical action on the water. Ehrenberg. Abhand. d. Berliner Akad. 1839, ' See Ehrenberg, " Die Infusionsthierchen," p. 106, Taf. I. II. Taf VIII. and IX. i Amblyophis, Euglena, Chlorosronium, SfC. 6 Gromia ßuviatüis, Miliola vulgaris, Vor- 2 Abliiindl. d. Berliner Akad. 1831, p. 12 ; als«, ticialis strigilata, Euglypha tuberculosa. Tri- " Die Infusionsthierchen," p. 491. nema acinus, according to Dujardin (Ann. des Ö 26 INFUSORIA AND RHIZOPODA. '$>'§> 11, 12. pigment,® for the blue, violet and green pigments, seen in the eyes of in- sects and Crustacea, show clearly that the red pigment is not essential to the eye* CHAPTER V. DIGESTIVE APPARATUS. § 11. The Infusoria are nourished, either by taking solid food into the interior of their body, or by absorbing by its entire surface nutritive fluids which occur in the media in which they live. This last mode is illustrated in the Astoma, which have no distinct oral aperture or digestive apparatus. By the ingenious experiment first per- formed by Gleichen,^^'' of feeding these animals with colored liquids, no trace of these organs could be found. Ehrenberg, who also had observed that they did not eat, regarded their internal vesicles as stomachal organs, which were in connection with the mouth by tubes. The correctness of this opinion, however, has not been verified. Indeed, the genus Opalina'^^'' refutes it ; here the species are quite large and visible to the naked eye, yet an oral aperture can be detected up- on no part of their body, and never do they admit into its interior colored particles. Solid substances found in them cannot be regarded as food. That fluids are here introduced by surface-imbibition is shown by Opalina ranar^'m; this animal is found in bile in the rectum of frogs, and assumes a green color. When Opalina requiring only a certain quantity of liquid are placed in water, they quickly absorb it, become greatly swollen, and shortly after die. In such cases, the absorbed liquid is seen as clear, vesicular globules under the surface, and these globules have been taken by Ehrenberg as stomachal vesicles (ventricüli), and by Dujardin as TACÜOLAE. §12. Those Infusoria which are nourished by solid food have a mouth at a cer- tain place, and an oesophagus traversing the parenchyma of the body. Through this last the food is received, and is finally dissolved in the semi-liquid parenchyma of the body, without passing through stomachal or intestinal cav- ities. In many cases there is at the end of the body opposite the mouth an ANÜ3, through which the refuse material is expelled. But, when this is 8 " Die Infusionsthiep;hen," p. 492. 2 The genua Opalina was first established by 1 Auserlesene iiiikrüskopische Entdeckungen, Purkinje, if Valentin. Many species are found 1777, p. 51 ; also, Abhandlung über die Saameu- in the rectum of frogs, and it is not rare to meet und Infusionsthierchen, 1778, p. 140. with them in the alimentary canal of Planarieae.t * Some recent researches of Thuret (Ann. d. Sc. fact is a very interesting one in this connection. — Nat. 3rd ser. XIV. 1850) on the reproductive germs Ed. of Algae prove that these bodies have red eye- t [ § H, note 2.] According to Affossiz (Amer. like specks, resembling those seen in the Polygas- Jour. Sc. XIII. 1862, p. 425), Opalina is only a trica, but which disappear when the Zoospores at- larval form of Distoma. — Ed. tach themselves and germination proceeds. The § 12. INFUSORIA AND RHIZOPODA. 2T ■wanting, its function is often performed by the mouth. According to Ehrenberg, the Infusoria polygastrica, such as we have just been describ- ing, differ from the hifiisoria rotatoria, in having a great number of stom- achs, which connect by hollow peduncles with the mouth in the division Anentera, and with the intestine in that of Enterodela. This organiza- tion, which, from its high authority, has generally been admitted by natu- ralists, is not, however, met with in any infusorium.'^* The vesicular cavities in the bodies of these animals, and which have been regarded by Ehi-enberg as stomachal-pouches, never have a hollow peduncle, either connecting with the mouth [Anentera) or with the intes- tine (Enterodela). Indeed, it is doubtful if a digestive canal can be made out in these Infusoria. The vesicular, irregular contracting cavities of their body contain a clear liquid, evidently the same as that in which they live, which, with the Astoma, has been absorbed through the surface of the body. But, with those having a mouth and oesophagus, it is received through them, and taken up by the yielding parenchyma of the body. If the methods of feeding of Gleichen and Ehrenberg are employed, the colored particles are taken in by a vortical action of the water, caused by the cilia surrounding the mouth. This water, with its molecules, accu- mulates at the lower portion of the oesophagus, and so distends there the parenchyma as to cause the appearance of a vesicle. Thus situated, the whole has much the aspect of a pedunculated vesicle. But when, from contractions of the oesophagus, this water escapes into the parenchyma, it appears there as an unpedunculated globule, in which the colored particles still float. When the Stomatoda are full-fed in this manner, there appear many of these globules in vri-ious parts of the body; and thus sub- stances previously ingested are taken up and disseminated throughout the body. If the globules thus containing solid particles are closely aggregated, it sometimes happens that they fuse together ; a fact which proves that they are not surrounded by a special membrane. The solid particles of food of the Stomatoda, which are often the lower Algae, such as the Diatomaceae and Oseillatoria, and often other Infu- soria, are sometimes deposited in the parenchyma without being surrounded by a vesicular liquid.^ From observations made upon Amaba, Arcella and Difflugia, it appears that the ßhizopoda ingest their food like the Stomatode Infusoria. 1 Focke (Isis, 1836, p. 785) has already raised neck. ( Malleres Arch. 1839, p. 80 ; also Monats- doubts as to the existence in Infusoria of the bericht der Berliner Akad. 184i, p. 103.) But, de- stomachs described by Ehrenbe.r^. Ehrenberg tailed as they may be ( see iArenöec^ Abhandl. d. has also opponents in Dujardin (Ann. des Sc. Nat. Ber. Akad. 1830, Taf. 111.; 1831, Taf. III.; also "Die Zool. IV. 1835, p. 364 ; V. 1836, p. 193 ; X. 1838, lufusionsthierchen," Taf. XXXII. XXXVI. and p. 230; also Hist. Nat. des Infus. 1841, p. 57), in XXXIX.), they are not representations of nature. Meyen {Müller''s Arch. 1839, p. 74) and in Ry- The organ which in Trackeiius ovum has been mer Jones (Ann. of Nat. Hist. III. 1839, p. 105 ; taken by Ehrenberg ("Die Infusionsthierchen," also, " A General Outline of the Animal Kingdom," p. 323, Taf. XXXIII. fig. xiii. 1) for a branching di- 1841, p. 56). gestive tube, has always appeared to me only as a He has attempted to reply to the objections here solid fibrous cord, traversing the soft parenchyma urged by very detailed illustrations of the organ- of the body, and by its ramifications presenting a ization of the Polygastrica, made by him and fV^er- coarse meshed aspect. * Bailey (Amer. Jour. So. May, 1853, p. 341) imagine a bag made of some soft extensible mate- has recently published an account, accompanied rial, so thin as to be transparent like glass, so soft with numerous figures, of a new animalcule, which as to yield readily to extension when subjected to ]s 80 remarkable in this connection that I give here internal pressure, and so small aa to be microscop- hia description. He says : " If the reader will ic ; this bag, filled with particles of sand, shells of 28 IxVFUoORIA AND RHIZOPODA. «^^ 13, 11. §13. If the vesicular eavhies containing the liquid and colorless food of the Stomatoda be examined under the microscope by a horizontal central inci- sion, their contents appear colorless ; but by changing the focus, viewing alternately the convex and concave surfaces of the vesicle, the points of junction between the colorless globules and the parenchyma appear colored pale-red. This appearance, due to an optical illusion, might easily deceive one into the opinion that the vesicles which are really colorless are colored. From this it is probable that Ehrenberg has described Bursaria vernalis and Trachelius meleagris as having a red gastric juice. '^' The violet points which are found upon the back and neck of Nassula elegans and Chilodon ornatus are only collections of pigment granules, which, in the first case, are often absent, and in the second are often par- tially dissolved. This last violet liquid has been regarded by Ehrenher g^'^^ as a gastric juice resembling bile § 14. The solid particles of food, whether surrounded by the parenchyma or enclosed in a liquid vesicle, are moved hither and thither in the gelatinous tissue of the body, during the contracting and expanding movements of the animal. In some, the parenchyma with its contained food moves in a reg- ularly circular manner, like the liquid contained in the articulated tubes of Chara.*^^ In Lozodes bursaria *-' this circulation is remarkable, and of much physiological interest. Its cause is yet quite unknown, for in no case is it due to cilia, and it maybe observed in individuals entirely at rest. Ehren- berg,''^^ therefore, is incorrect in regarding it as due solely to a contratile power of the parenchyma, displacing the molecules. Much less is his ex- planation '^' satisfactory, since the digestive tube of an infusorium can be extended at the expense of its stomachal pouches, so as to fill the whole body, giving it the appearance of having a circulation of molecules through- out its entire extent. 1 " Die Infusionsthierchen," pp. 321, 326, 329. 1836, p. 786 ; also Meyen, Miiller's Arch. 1839, Ehrenberg lias, moreover, in Trachelius melea- p. 75. griSy coufiiuniled the contractile cavities with those - Focke loc. cit.; also Erdl, MüUer''s Arch. 1841, non-conlractile, anrl which receive the food. p. 278. 2 Abhandl. d. Berliner Akad. 1833, p. 179 ; also a Loc. cit. p. 262. " Die Infusionsthierchen," pp. 319, 338, 339.* 4 MuUer's Archiv. 1839, p. 81. 1 Vaginicola and Vorticella. See Focke, Isis, Diatomaceaj, portions of Algae or Desraidieae, and those of any animalcule with which we are ac with fra;,'nients of variously colored cotton, woolen, quainted. — Ed. and linen fibres, will give a picture of the animal ; * [§ 13, note 2.] In this connection should be to complete which, it is only necessary to add a noticed the experiments of }VUl (MüUer's Arch, few loose strings to the bag to represent the varia- 1848, p. 5U9). He found evidences of a biliary ap- ble radiant processes which it possesses around the paratus, with Vorticella, Epistylis, and Bursaria. mouth." This animal, which is often found with These evidences are based on chemical reaction, bits of cotton protruding from its mouth, assumes and he describes no anatomical apparatus. I men- tlie most bizarre shapes. They apjjear to multi- tion this fact here, although Vorticella belongs I)ly by Issaration and gemmation even when tilled truly to the Bryozoa, and Bursaria to the Plana- with tnese heterogeneous iiarticles, and, on the ria. — Ed. whole, present characteristics as remarkable a* ^-^t 15, 16. INFUSORIA AND RHIZOPODA. 29 §15. The round or elongated oval mouth of Infusoria varies as to its posi- tion. Sometimes it is in front, sometimes behind ; and in some cases, near the middle third of the body. Rarely naked,''' its borders are generally ciliated,*^' and often its circumference is provided with a very remarkable ciliary apparatus. By the aid of this, these animals not only move about, but when quiet produce vortical actions of the water, which are felt at quite a distance; and all minute particles within its reach are quickly drawn towards its mouth, and then swallowed or rejected according to the option of the individual.'^' It is rare that this oral aperture is provided with a dental apparatus.''** The oral cavity, generally infundibuliform, extends into a longer or shorter, straight or curved oesophagus, which is lined throughout by a very delicate ciliated epithelium.'^' The anus, situated usually upon the dorsal surface of the posterior por- tion of the body, is sometimes, though rarely, indicated by a slight exter- nal projection.'"' CHAPTERS VI. AND VII. CIRCULATORY AND RESPIRATORY SYSTEMS. § 16. A vascular system entirely distinct by closed walls from the other organs is not found in the Protozoa. But with very many (with all the Stomatoda, without exception) there are contractile pulsatory cavities, the form, number and arrangement of which is quite varied. They are situated in the denser and outer layers of the parenchyma of the body, and during the diastole they become swollen by a clear, trans- parent, colorless liquid, which, during the systole, entirely disappears. 1 Actinophrys. The mouth is naked also in the while it is long and arcuate in Bursaria trunca- genera Diffliig^ia and Arcella of the Rhizopoda.* tetla and cordtformis. 2 Bursaria, ParamcBcium, Uroslyla and Sty- « The undigested matters accumulate about the lonychia. In Glaucoma scintiUans the ciliated anus, and when this opens are expelled from the crown of the mouth is replaced by a special semi- parenchyma with a certain force. With Nnssula lunar ciliated lobe. elegans, the greater or less portions of the Oscil- ^ In Stentor, Forticetla, Epistylis und Tricko- latoria graciltima {Kulzing) upon which it dina, this apparatus is retractile, and produces in a feeds, and which are of a blue-green color, dis- particular way the vortical actions. In Sjiirosto- solve into granules of this color. But these, dur- mum ambiguuin, there is a long, narrow, ciliated ing the process of digestion, gradually assume a furrow, through which the food is conducted to the brown color, and form irregular masses in the pos- mouth, situated at the posterior portion of the body, terior portion of the body, and are from time to < Prorodon, Nassu/a, Chilodon and Chlamido- time expelled as brown foeees. These green gran- don. Here the hair-lil1(3 teeth are arranged in a ules are not therefore eggs, as Ehrenberg ( loc. cylinder so as to resemble a weir. cit. p. 339) has supposed. This Nassula when 6 The oesophagus is short in Oxytricha, Sty- young is perfectly colorless, with the exception of lonychia, and Euplotes ; but is elongated or spl- a beautiful blue spot. ral in Forticella, Carchesium and Epistylis ; * r § 15, note l-l Källiker (Siebold And Kolli- stance. Yet this remarkable animal lives on other ker''s Zeitsch. 1. 1849, p. 198) has given a long and Infusoria, Algae, &c., and avails itself of them by detailed description of Actinophrys sol. Accord- seizing and afterwards invaginating them in its pa- ing to him, it is without mouth or stomach proper, renchyma, until they finally are included within ita and internally is composed of a homogeneous sub- interior. — Ed. 3* 30 , INFUSORIA AND RHIZOPODA. . <§, 17. These movements succeed each other at more or less regular intervals. When these cavities are numerous, a certain order in the succession and alternation of their contractions cannot always be observed. It is very probable that their liquid contained during the diastole is only the nutri- tive fluid of the parenchyma, and to which it returns during the systole. In this way it has a constant renewal, and all stagnation is prevented. This arrangement constitutes the first appearance of a circulatory system, and the^rs^ attempt at a circulation of nutritive fiuids. From an optical illusion similar to the one mentioned as belonging to the vacuolae C^ 13) the liquid of these pulsating cavities has a reddish hue.'" § n. A round, pulsating cavity is found in the genera Vorticella, Epistylis, Loxodes, and in the following species: — Amaiba diffluens, Faramcecium kolpoda, Styloriychia mytilus, Euplotes patella, 8fC. With Actinophrys, Bursaria, Trichodina, there are from one to two ; with Arcella vulgaris, three to four ; with Nassula elegans, there are four placed in a longitudinal line on the dorsal surface. With Trachelius meleagris, there is a series of eight to twelve upon the sides of the body, and with the various species of AmpMleptus there are fifteen to sixteen arranged more or less regularly. With Stentor, there is a large cavity in the anterior portion of the body, and many similar cavities appear upon the sides, united sometimes into one long canal. A similar canal traverses the entire body of Spirostomum ambiguum, and Opalina planariarum. With Faramcecium aurelia, the two round cavities present a remarkable aspect, being surrounded by five or seven others, small and pyriform, the top of which being directed outward, the whole has a star-like appearance.'" During the pulsation, often the entire star disappears, sometimes only the two central cavities, and in some cases the rays only. These cavities, entirely disappearing in the systole, reappear in the dias- tole, and usually in the same place and with the same form and number. This would lead us to conclude that they are not simple excavations in parenchyma, but real vesicles or vessels, the walls of which are so excess- ively thin as to elude the highest microscopic power. In some individuals, as, for instance, with Trachelius lamella, there appear, during the diastole, two or three small vesicles at the extremity of the body, which, after having increased in size, blend into one which is very large. These are probably only globules of nutritive fluid, separated from the parenchyma. Similar phenomena are observed in Phialina ver- micularis and Bursaria cordiformis. It sometimes happens with these animals that a forcible contraction of the whole body divides an elongated cavity into two spherical portions, as 1 Ehrenbersr (loc. cit. p. 321, Tiif. XXXIEI. fig. in the body. It really seems very strange that viii.), deceived by this illusion, liiis taken the ei],'ht these animals should practise uninterruptedly these to twelve CDUtrac.tile cavities of YVacAe/tM,? ?ne/ca- pollutions throughout their entire life. These ani- on's for gtomachal cells, filled with red gastric juice, nials have neither testicles nor ovaries, and the lie has also regarded these cavities, when simple or function of these cavities is not, therefore, that double, as seminal vesicles. (Abhandl. d. Iterliner assigned to them by fChrenben;, — but is, as I Akad. 1833, p. 172,-1835 p. 158.) In species Hunk, with /r/eirmaHn CArch. f. Naturg. 1835, I. having but few, he has very arbitrarily decided that p. 12), ana^l^•ous to that of a heart, someareseminal vesicles, others stomachal pouches, ^ JJujardin, Ann. d. Sc. Nat. Zoo], tome X. PI. as, for example, in Am/j/iileptus (loc. cit. p. 355). XV. fig. 3; also, " Infusoires," PI. VIII. fig. 6. According to him, the seminal vesicles, upon con- Elirenberg's plates of these star-like vesicles ar» traction, pour the sperm upon the eggs contained incorrect. <§>«§. 18, 19. INFUSORIA AND RHIZOPODA. 31 though it were a drop of oil. The observation of these phenomena would make it doubtful whether or not these cavities are true vesicles or vessels. These cavities have been met with in only a few of the Astoma, and these are, Cryptomorms ovata ^^' and Opalina plariariarum. § 18. The Infusoria appear to respire solely by the skin. In those species whose bodies are covered with vibratile cilia this function is promoted by the vortical action of the water caused by these organs. In others, the contractile cavities just described are situated immediately under the skin^ and the opinion may be entertained that tlie water so communicates with their liquid contents as to perform a respiratory function. In this re- pect Acthiophrys sol is quite remarkable, for its contractile cavities are so superficial that when filled they raise the skin in the form of aqueous vesicles,*^' which, however, are so elastic as entirely to disappear in the parenchyma. Here it is plain that a mutual relation between the external water and the contents of these cavities might easily take place. CHAPTER VIII. ORGANS OF SECRETION. § 19. No special organ of secretion has been found in the Protozoa ; their skin, however, has a power of secreting various materials, which in some species harden and form a carapace, or a head of a particular shape ; while in others it serves to glue together foreign particles, forming a case, in which the animal retreats. Among those having a carapace, may be mentioned Vaginicola, Cothur- nia, and Arcella. This more or less hard envelope does not resist fire, and is probably of a corneous nature. In the Rhizopoda, however, it is usually calcareous, like the shells of Mollusca, and is not affected by heat. The Difflugiae carry about with them an envelope of this kind, composed of grains of sand. 2 Ehrenberg, loo. cit. p. 41, Taf. II. fig. xvii. 1 Ehrenberg (Ibul. p. 303, Taf. XXXI. flg. vi. 1 ) appears to have taken the protrusion of these coB» tractile vesicles for that of a snout. 32 INFUSORIA AND RHIZOPODA. ^^ 20, 21, 22:. CHAPTER IX. ORGANS OF REPKODUCTION. § 20. The Infusoria propagate by fissuration and gemmation, and never by eggs.*^^ They have therefore no proper sexual organs. This fissuration occurs longitudinally with some,® transversely with others/^' and in many of them by both at once.'^' Gemmation, on the contrary, is very rare.*^^ § 21. Nearly all the Infusoria and Rhizopoda have in their interior a nicely- defined body, a kind of a nucleus, which is quite different, in its compact texture, from the parenchyma by which it is surrounded. This nucleus, which, in different species, varies much in number and form, performs an essential part in the fissuration. For, every time the individual divides either longitudinally or transversely, this nucleus, which is usually situated in the middle, divides also. So that, in the end, each of the two new individu- als has a nucleus. When an animal is about to undergo fissuration, there is generally first perceived a change in the nucleus. Thus, in Parai?ioecium, Bursaria and Chilodo?i, the nucleus is sulcated longitudinally or trans- versely, or even entirely divided, '^^ before the surface of the body presents any constriction. This nucleus, which is of a finely granular aspect and dense structure, re- tains perfectly its form when the animal is pressed between two plates of glass, and the other parts are spread out in various ways. By direct light its color appears pale yellow, it appears to lie very loosely in the parenchyma, and sometimes individuals may be observed turning their bodies around it as it rests motionless in the centre. From all this, it cannot be supposed that this nucleus attaches itself to other parts of the animal, and especially to the pulsatory cavities (Vesiculce seminales o^ Ehrenberg). '-'^^ § 22. A simple, round, or oval nucleus is found in Euglena, Actino'phrys, Arcella, Amcuba, Bursaria, Paramoicium, Glaucoma, Nassula and Chilo- dmi. But there are two which are round, and placed one after the other in AmphUeptus armer and fasciola, in Trachelius meleagris, and Oxytri- cha peiliondla. With Stylomjchia mytilus, there are four. 1 That which Ehrenbe.rc; has arbitrarily taken 3 This may be easily observed with Stentor, for eggs is sometimes granules of the parenchyma Leucophrijs, Loxoitex, anil Bursaria. or pigment corpuscles, sometimes bits of food. He •• liur.taria, Opaliiia, Glaucoma, Chilodon, Pa- did not perceive that these bodies wantall that which ramiecium, Stylonychia and Euploten. is necessary to make up an egg, — such as chorion, 6 yorliceUa, Carchesium and Epistylis. vitellus, and germinative vesicle and dot. It is on ^ Ehrcnberg,\oc. ci\.. Taf. XXXVI. fig. vii. IS this account that he declares that he never has to 19, Taf. .XXXIX. fig. ix. 4, 5, 11-13. observed the hatching of young Infusoria. (Ab- - Elirenberg, from a strange fancy, has taken iandl. d. Berliner Akad. 1835, p. 156.) this nucleus for a seminal gland. (Abhandl. d. 2 yorticeUa, Carchesium. Berliner Akad. 1835, p. 163. Also, loc. cit.) <^23. INFUSORIA AND RHIZOPODA. 8S It is not rare that a variable number of these round nuclei, arranged in a row, traverse the body in a tortuous manner. This is so in Stellt or coendeus and poly mo7-phus, in SpirostomuTn amhii^iaim, and in Tradtelhis vioniliger. In man}' instances the nucleus has the form of an elongated band, which is slightly curved in Vorticella convallaria, Epistylis leucoa, Prorodon niveus- and B^crsaria truncatella. In Stentor RcBselii, it is spiral, and in Enplotes patella and Trichodina mitra, it is shaped like a horse-shoe. In Loxodes bursaria, it is kidney-form, and encloses in one of its extremities a small corpuscle (nucleolus). The round nucleus of Euglena viridis has in its c.entre a transparent dot. In Chäodo7i cucullulus, the nucleolus has a similar dot, and thus tha nucleus as a whole resembles a cell. § Z6. These nuclei, which make Infusoria resemble cells, deserve a special attention, since they do not die with the animal. Thus the nucleus of Euglena viridis, which, according to Ehrenher g,'-^'' is globular when dying, and surrounded by a kind of cyst, remains unchanged a long time, or even increases in size, having no appearance of a dead body. It may be that the life of this animal, under these circumstances, is not finished, but only assumes another form.'-' 1 Loc. cit. p. 110. Ttiat the nucleus contained in Infusoria plays an 2 Perhaps this nucleus, of which the animal is important part in the propagation of those animal- only a temporary envelope, is ultimately develuijed «ules, is supported also l)y a recent observation of into a particular animal. Indeed, perhaps this Focke, who witnes.sed the development of several species, as well as many others, are only the kirVäl' 'yodng individuals in the nucleus of Loxodes bur- states of other animals, whose metamorphoses are saria. See Amll. Bericht über die 22 tr. Versaaml. yet unknown. It may jiroperly be asked, if this deutsch. Naturforscher, in Bremen, Abth. ii. p. nucleus has not, relative to the body containing it, 110. the same significatiou as have the tubulous larvie of Monostomuin mutabile (see below) to the em- bryos tUey surround. INTRODUCTORY NOTE TO THE ZOOPHYTA. Within the past sis or seven years the Zoophytes have received more attention from naturalists than any other division of the animal kingdom. The labors of many, if not most of our ablest naturalists, have been directed towards an investigation' of the humblest forms of_ animal life. This fact, combined with the recent improved methods and means for research, would alone be prophetic of the most signal advances in this gi-oup ; indeed, our knowledge of all these forms has been so modified, as well as increased, that previous writings need rather to be re-written than revised. Dana, Agassiz, Milne Edwards, Forbes, Dalyell, Midler, Busch, and others, not to mention the continued labors of older observers, have eflfected these changes in this group. The work of Dana is most excellent, and will remain a standard of au- thority in this department for a long time to come. Aside from the many details of structure, in it may be found the first and best philosophical exposition of the relations of organic development with these lower plant- like forms. Had this work been better known in Europe, there would have been saved the constant repetition of the most grave errors. On the labors of Agassiz no comment need be made ; those who are in this department, whether as minute Anatomists or philosophical Zoologists, will not fail to understand and appreciate him. In the same field is Busch, who was extended his brief though excellent labors over the three classes of this whole group ; as for the remaining authors mentioned, excepting Midler, their position in this department has long been established. Midler's researches have been mostly on the Ecliinoderms, and the careful tracing of the phases of their development and metamorphoses; but where so much has been done, I fear the limits of this book will preclude full details with this class. This note would be unnecessary, were it not to show that I do not ignore the changes and advance which have been made in this group within the past few years ; and more especially so, as I have allowed, in this edition, the classification to stand as in the original. Any great changes of this INTRODUCTORY NOTE TO THE ZOOPHYTA. 35 kind I could not think of making without the consent of the authors, who, although thej would undoubtedly fully sanction them, are not sufficiently accessible to me just now, as these pages are going to press. So, however much the present classification may ofiend the eye of the Zoologist, yet the Anatomist will find under each head the proper details. Thus, he will find as full a description of the anatomical structures of the Bryozoa and Hydroid Polypi, as though they were referred to the Mollusca and Acal- ephae, where truly they respectively belong. Editor. BOOK SECOND. POLYPI. CLASSIFICATION. § 24. The Polypi are either immovably fixed, or seated on a locomotive foot. Their soft body is in part enveloped by a solid support, the polypary. This last is often, for the most part, horny or calcareous ; and by it numbers of these animals are united into greater or less groups. The central mouth is always surrounded by a coronet of contractile tentacles. The digestive apparatus is organized after two different types, upon which is based a division of these animals into two orders. The sexual appara- tus is always without copulatory organs. ORDER I. ANTHOZOA. The digestive canal is without an anus, and opens into the general cavity of the body. Family : Madreporina. Genera : Ocidina, Millepora, Madrepora, Caryophyllia, Astraea, Besmo- phyllum, Maeandrma, Wlonticularia, Agaricia, Favia. Family : Gorqonina. Genus : Gorgmiia. Family : Isidea. Genera : Corallium, Isis. Family: Tubiporina. Genus : Tuhipora. Family : Alcyonina. Genera : Alcyonium, Lobvlaria, Alcyonidium. Family : Pennatulina. Genera: Veretillum, Pennatula, Virgidaria. ^ 24. THE POLYPI. Family : Sebtulakina. Genera : Sertularia, Campamdaria. Family : Zoanthina. Genus : Zoanthus. Family : Hydrina. •Gsnera' Hydra, Eleutheria, Synhydra, Coryne, Syncoryne, Corymorpha, Family : Actinina. Genera : Actinia, Eumenides, Edioardsia. ORDER IL BRYOZOA. The digestive canal is closed from the general cavity of the body, and opens behind through an anus. Family: Reteporina. Genera : Eschara, Cellepora, Flustra, Bicellaria, Retepora, Telegraphina, Tendra. Family : Alcyonellina. Genera : Cristatella, Alcyonella, BowerbanJcia, Vesicidaria, Lagenella, Plumatella, LßphopusS^^ BIBLIOGRAPHY. Ellis. Essai sur THistoire naturelle des Corallines et d'autres produc- tions marines du meme genre. La Haye, 1756. Pallas. Elenchus zoophytorura. Hagae 1766. Cavolini. Memorie per servire alia storia dei polipi marini. Napoli, 1785. Rapp. Ueber die Polypen im Allgemeinen und die Aktinien insbeson- dere. Weimar, 1829. Ehre7iberg. Die Corallenthiere des rothen Meeres, in the Abhandl. d. Berliner Akad. 18.32. Joh7iston. A History of the British Zoophytes. Edinburgh, 1838. Besides the important work of Dana, which will be often quoted in my notes, the additions to the literature of the true polyps have been few since the issue of this work, and have generally been published in the form of articles in the various periodicals, to which reference will be made in my notes. But the Bryozoa have been specially studied, and particularly in the following papers : 1 There are here enumerated only those families This remark applies equally to the following whose organization has been speuially studied, classes. 4 38 THE POLYPI. ^§ 25. 26. Van Beneden. Reclierches sur I'Anatomie, la Physiologie et le devel- oppement des Bryozoaires. Mem. Acad. Erux. Tomes XVIII. XIX. Kecherches sur les Bryozoaires fluviatiles de Belgique. Ibid. Tom. XXI. For further literature on the Bryozoa, see the writings quoted in my notes, and especially those of Allman. Ed. CHAPTER I. CUTANEOUS ENVELOPE AND SKELETON. § 25. The Polypi are composed of either entirely soft parts,* or have for their support a solid frame, which may be calcareous, corneous, or coriaceous. This frame is always the product of the general skin, and ought therefore to be compared to a cutaneous skeleton.* This skeleton, known by the name of polypary, is formed partly internally, and partly externally, by these animals. In the first case it is called an axial, and in the second a tubular polypary. The axial polypary consists, with some polyps,® of a dense substance, apparently unorganized and composed of carbonate of lime ; with others,*^' of a corneous substance, equally unorganized. When the polypary is coriaceous, it is often covered by a variable number of calcareous, fusiform corpuscles, usually bossed or dentated.'^' With some calcareous polyparies *^' this is also true, and then the corpuscles are arranged in compact reticu- lated masses. The tubular polyparies serve as a refuge for the animals living in them, and in many cases, being common to many individuals, these last are in direct relation to each other by the canals which traverse the branching tubes. In the axial polyparies there are often cavities or depressions of a variable size,'''' in which the animals can conceal them- selves. When, however, these are wanting,'*^' they retire, as is the case with many soft polyps,® beneath their mantle. Sometimes,*'*' these cavities are closed by a movable operculum. § 26. The skin of polyps is very transparent, and should be carefully dis- tinguished from the parenchyma which it envelops. It is smooth, or it is covered with ciliated epithelium. And, since it has been shown that many 1 The Actinina and Ilydrina. p. 403, Taf. I.-III.) has described and figured these 2 Coral/iiim. spicula under the names of Sponsolithis and 8 The Gorgonina. hithostij lidium. * These corpuscles are easily seen in Alcyonium 5 The Madreporina. and Lobularia. {Milne Edwards, Ann. d. Sc. 6 MiUepora, Mfulrepora, Orulina Sini Astraea. Nat., Zool. IV. 1835, pi. XIII. fig. 9 ; PI. XV. fig. '^ Gorgonia, Isis and Corallium. 10—11.) Spicula of this kind are found in the S The Actiniae. interior of their tissues, as well as on the surface. 9 Eschara and Cellepora. Ehrenberg (Abhand. d. Berl. Akad. 1811, Th. I. * It should here be remarked that the old, and with Madrepora, Astraea, (fC. For the formation as now regarded, mistaken view of the formation of of Coral, see Datia, loc. cit.; and for the relations of the frame of Polyps is here repeated ; for the frame the corallium carried out in detail, see Edwards and is generally an internal skeleton, as. for instance, Haime, Ann. d. Sc. Nat. 1849, '50, '51. -r- Ed. <§>§ 27, 28. THE POLYPI. 39 Anthozoa have the skin, and especially the tentacles, covered with cilia of this nature,*'' these last cannot be regarded as forming a differential charac- teristic between them and the Bryozoa, as has been done by EhrenbergS^^ § 27. The skin of many polyps is quite remarkable in having nettling or poisonous organs, to which it is only of late that the attention has been directed. They consist of transparent vesicles, having a dense membrane, of a round, oval, or cylindrical form, containing a clear liquid, and a very delicate filament of variable length, which is usually spirally coiled. By the least irritation of the skin, the filament is thrown out of the vesicle, of which it appears to be only a prolongation. These filaments adhere to objects coming in contact with the skin, and in this way the vesicles in question are separated from it.'^' These organs are probably the cause of the nettling sensation felt when certain polyps are handled. § 28. Still more interesting are organs analogous to those just mentioned, and which belong to various species of Hydra.'-^' They are found not only on the arms, but also upon the skin of the body and foot. They consist of oval vesicles, having a very long and delicate filament, which is slightly swollen and viscous at its free extremity, while the opposite one is directly continuous with the conical neck of the vesicle. The neck of each vesicle is surrounded by three hooks curved backwards. These are always elevated when the skin of the animal is irritated, and especially that of the arras when they seize their prey. This last is then wound about by the free, viscous end of the filament, and the attached vesicle being torn from the body, the whole is often entangled in the arms of adjacent polyps. When this occurs, the vesicles hang by their hooks to the arms of the polyps ; and it is this that has given Ehrenberg the opinion that the vesicles are detached by their round extremity, that these animals watch their prey with the hooks erected, and that the vesicles and filaments can return into the inte- rior of the arms.'-' But it is probable that they (the hooks) act more- as poisonous than as prehensile organs ; for if those from the arm of a Hydra seize upon a Nais, a Dajjhnia, or a larva of Chironomus, these last quickly die, even if they escape immediately after being taken. 1 KtM has seen very distinct ciliated epithelium (Ehrenberg), I have seen these cylindrical organs in Actinia and f^eretillum. (See Miiller's having a long spiral filament. With Ed wardsia, Arch. 1841, p. 423.) Quatrefaa:es has found these organs upon the '■i Abhandl. d. Berl. Akad. 1834, p. 255, 377. whole surface of the body, as well as upon the 1 These nettling organs, which are much more arms. (Ann. d. Sc. Nat., Zool. 1842, XVIII. p. 81, common in the lower orders of the animal kingdom PI. II. fig. 4-6.) For the nettling organs of the than was at first supposed, are yet quite imper- Tubvlariae andthe Actiniae, see a]so Wagner in fectly known. Wagner first discovered them in Mül/er''s Arch. 1847, p. 195, Taf. VIII. the Actinia, although he regarded them at first 1 These were first described by Ehrenberg. as the spermatic particles of these animals. {Wieg- (Mittheil. a. d. Verhandl. d. Gesellschaft naturf. mann''! Arch. 1835, II. p. 215, Taf III. fig. 7, also Freunde zu Berlin 2 tes. Quartal, 1836, p. 28 ; also, ■■841, I. p. 41 ; IconesZoot. Tab. XXXIV. fig. 24.) Abhandl. d. Berl. Akad. 1835, p. 147 ; 1836, p. These researches have been extended by Erdl, 133, Taf. II.) They have been carefully studied whohasshownthat they also exist with Fcre?j7/«TO by Erdl {MüUer''s Arch. 1841, p. 429. Taf. XV. and Alcyonium. {Mailer's Arch. 1841, p. 423, fig. 10-13). Taf. XV. tig. 3--6 and 8, 9.) In Alcyonium, Erdl 2 Ehrenberg has figured, ideally (Abhandl. d. has observed the filament take, on its departure Berl. Akad. 1836, p. 133, Taf II. fig. 1) an Hydra from the vesicle, first a riband-like, and then a in the act of seizing its prey with extended hooks, spiral aspect. In Desmophyllum stellaria In reality this animal is never thus seen. 40 THE POLYPI. ^28. These poisonous and prehensile organs are destroyed by use, which is also true of the nettling organs. But this loss is probably repaired by their speedy reproduction. This last circumstance may explain the various descriptions given them by different authors, for, probably they have been observed at dissimilar stages of development.*'^' 8 Erdl, who has discovered a great number of these nettling organs, saw, in some cases, the thread -directly continuous with the neck of the vesicle ; in others, these necks appeared furnished with spines directed backwards •, exactly as Warner had before described, and as Kiilliker had often ob- * [§28, note 3.] These nettling organs of the Polypi have recently been very successfully studied by Agassiz, who has enjoyed the most enviable advantages with the Polypi and Acalephae of the North American coast. He has changed the entire aspect of the subject, besides almost exhausting it for future research. His special studies were made on the coral polyp of our southern coast, the Astrangia Danae, Agass. The complexity of structure of these lasso-cells, as he has very appropriately termed them, is truly wonderful for such minute forms. As I have also studied these forms, I will use my own language, in the description of what Pro/. Agassiz has seen. There are several varieties of these cells or capsules, depending upon the ar- rangement and structure of the lasso ; sometimes this last is a simple coil, sometimes it is coiled about s. staff which is erected from the base, but which is also a part of the projectile apparatus. In the first case, the lasso is much the longer and may be fifty or seventy-five times the length of the vesicle; while, in the second case, it rarely exceeds the length of this last by more than sixteen or twenty times. In all cases, the essential feature of these organs is the Jasso or internal coil, which is of a most curious structure. In the first place, it is, in general terras, only an inverted portion of the vesicle or cell itself, an internal instead of an external cilium, coiled up in a regular manner. When thrown out, there- fore, it is wholly inverted, and its projection consists of an instantaneous tui'ning of the whole inside out. But the lasso, delicate as it is, lias still more delicate structures on its surface. These consist of barbels arranged in regular spiral rows, which extend to the very extremity of the lasso. At this last served (Beiträge z. Kenntniss d. Geschlechtsver- hältnisse u. d. Samenflüssigkeit wirbelloser Thiere, 1841, p. 44, fig. 14). Erdl asks if these variations of form are not coincident with an increasing or decreasing activity of the sexual organs (see Mailer's Arch. 1842, p. 305). * point, they aUnost elude the highest and best micro- scopic powers. These barbels all point backwards when the lasso is extended, and serve, no doubt, as teeth, to prevent it from slipping on the objects ovei which it is thrown. But these most delicate struc- tures, which in beauty transcend that of all other tissues, can be better appreciated by figures than by the most minute description ; see Agassiz's Memoir on Astrangia Danae (forthcoming in the " Smithsonian Contributions to Knowledge"), PI. VI. These observations, however, were made in 1848 ; see Proceed. Amer. Assoc. Advancem. Sc. 1848, p. 68. From my own observations there would, indeed, be nothing to add on the special points studied by Agassiz ; but a remark or two may be made as to the development of these forms. The lasso-vesicle is, originally, only an epithelial cell, of a spheroidal shape. It soon elongates, its contents become cloudy, after which, the coil i3 seen, very faintly marked, lying on the inner wall. It would seem probable, therefore, that its forma- tion was somewhat similar to that of the spiral vessels in plants, although it is true that the lasso- coils and these spu-al vessels are analogous only iti form and position, and not in structure. The details of the formation are unknown. These lasso-cells are more widely distributed among the Radiata than hitherto supposed. Agas- siz (as he has informed me by letter) has observed them on most of the Polypi and Acalephae, and even with some of the Mollusca, and although their general structure is the same, there are points of difference of even a zoological value. Editor. •^.'S» 29, 30. THE POLYPI. 41 CHAPTER II. MUSCULAR STSTEM AND ORGANS OF LOCOMOTION. §29. The movements of Polyps are pei-formed, partly by contractions of the sides of their body, in which are found no muscular fibres, and partly by a true muscular tissue. The fibres of this tissue have not regular trans- verse striae, although during their contractions there are sometimes, though, I'arely, seen irregular transverse bands. ^'^ §30. In those Polyps having a true muscular system, this tissue is composed of interlaced fibres, forming a layer beneath the skin. A coarse net-work of this kind is seen in the arms of Hydra, although in the foot and rest of the body there is scarce anything comparable to muscular fibres. ^^' Under the skin of Synhydra'-'-^ and in the arms of ELcutheria^''^ this muscular system is much more apparent. A similar layer, very distinct, is observed in Acti- nia, which, in their mantle, is composed of both longitudinal and circular fibres, the contraction of which draws the tentacles together, and this, com- bined with that of the radiating fibres of the foot, gives rise to the various forms of these animals.*^' The Bryozoa have the muscular system more apparent; in the cavity of their body completely isolated fasciculi are seen, composed of parallel .fibres, serving especially for the withdrawal of these animals into their cells. These fasciculi arise from the internal surface of the body, and are inserted partly into the base of the tentacles, and partly into the neck and digest- ive canal, — thus serving almost exclusively as retractors of these last.® 1 Milne Edwards, who declares he has seen 2 Quatrefagc.i, Ann. d. Sc. Nat. XX. 18-13, p. striated muscular fibres in Esckara (Ann. d. Sc. 238, pi. IX. fig. 3-5. Nat. VI. 1836, p. 3), must have been deceived. I 3 quatre/ages, Ibid. XVIIL 1842, p. 281, pL have been unable to perceive them in Esckara, ÄI- VIII. tig- 3. cyonella, Cristaiella, and other species. Iford- ■* Bertko/d, Beitr. zur Anat. u. Physiol. 1831, p. mann also has not found them in Cellaria. (Ob- 16 ; also in the body of Edwardsia, Quatre/a^es serv. sur la Faune Pontique, 1840, p. 679 ; also has found longitudinal and circular fibres (Ann. d. Muller's Arch. 1842, p. ccviii.) The irregular bands So. Nat. XVIII. p. 84). appearing during contraction, but afterwards disap- 5 Similar muscles have been observed by Farre pearing, have been observed by Quatrefases with (Phil. Trans. 1837, p. 387) iu Bowerbankia, Vesi- Edwardsia (Ann. d. Sc. Nat. XVIII. 1842, p. 84, cutaria, Lasenella and other Bryozoa. Milne pi. II. fig. 7, a-b).* Edwards has seen them in Tubulipora and Es- 1 Corda, Nov. Act. Acad. C. L. C. Nat. Cur. chara. (Ann. d. Sc. Nat. VIII. 1837, p. 324 ; VI. XVIII. 1839, p. 299. Also Ann. d. Sc. Nat. VIII. 1836, p. 23, pi. I. fig. 1, c, 1, d ; pi. II. fig. 1, a.) J837, p. 363. Coste has given a very detailed descriptiou of the * [ § 29, note 1.] Busk has described and figured cies examined no such form of muscle is present, the striated form of this tissue with Anguinaria Quite lately, however, the subject has beep care- spatulata and Notamia bursaria. (Trans. Micro- fully e.xamined by Allman (Rep. Brit. Assoc. 1850, scop. Soc. of London, II.) I have been unable, p. 318), and his descriptions are such as to leave however, after considerable search upon many Bry- no doubt upon the existence of the striated fibre ozoa, among which were several Alcyonella, to wilt the species he has examined, among which detect any appearances of this kind; and I would are he Paiudirdlae. — Ed. venture a pretty confident opinion that in the spe- 4# 42 THE POLYPI. §^ 31, 32. With Eschar a there are, moreover, two fasciculi in each cell, which movö its operculum, and thus close the entrance of this cavity Z*'' §31. Locomotion is performed bv the Polyps in various ways. With the Hydrae, by their long-stretching arms ; with Actiniae, by the contractions of the disc of their foot ; ^" while the Edwardsiae, having elon- gated bodies which are not attached by a foot, progress by vermiform movements.*-' With Cristatella mirabilis, the whole colony moves itself along by the foot-like basis, like the Actiniae.^'^ Some Polyps, at a certain period of their development, move freely in the water by discoid contractions of their body, like the pulmograde Acalephae.'^' § 32. A very remarkable peculiarity is the presence, in certain Bryozoa, of organs shaped like a bird's head, and which swing to and fro at the base of their cells. In some species, these organs have the form of lobster's claws, being composed of both a fixed and a movable piece. This last is corneous, and moved by a muscle which arises from a cavity in the first. It is not yet known by what means either this beak is opened, or the whole organ moves to and fro.*^' Equally unknown is the function of these singular organs, the move- ments of which persist after the death of the animal, and of which, there- fore, they are independent. *^> They are perhaps organs of defence or pre- hension, and analogous to the Pedicellarice of the Echinoderms. muscles of Plumatella (Comp. rend. XII. 1841, p. 724 ; Mailer's Arch. 1842, p. cc.\).* B Milne Edwards, Anu. d. So. Nat. loc. cit. p. 24, pi. I. fig. 1, e. 1 Berthold, loc. cit. p. 14. 2 qaatrefages, Ann. d. Sc. Nat. XVIII. p. T4; also Forbes, Ann. of Nat. Hist. VIII. 1842, p. 243. Ü I have been able to confirm the observation of Dalyell (Froriep's Notizen 1834, No. 920, p. 276) upon this motion in Cristatella. Trembley, also, has observed that the corallura of Plumatella cristata moved half an inch in eight days (see liis jM^moire pour servir a I'Hist. des Polypes d'eau douce, 1775, p. 298). 4 See the observations of Steenstrup (Ueber d. Generationswechsel, 1842, p. 20) upon Coryne fri- titlaria ; also those of Van Heneden (Mem. sur 143 Campaiiulaires, 1843, \i. 29, or Froriep's neue Noti- zen, 1844, No. 663, p. 38) upoa Campanularia ge- latinusa. * [ § 30, note 5.] Allman (Report Brit. Assoc. 1850, p. 314) has described a very complete mus- cular system in the fresh-water Bryozoa. In the species with bilateral lophophores, there are seven distinct sets : 1. Retractor muscles of the polypide; 2. The rotatory muscles of the crown ; 3. The tentacular muscles ; 4. The elevator muscle of the valve ; 5. Superior parieto-vaginal muscles ; 6. Inferior parieto-vaginal muscles ; 7. Vaginal sphinc- ter. The walls of the stomach also contain circular muscular fibres. 1 These organs were first described by Ellis (Essai sur I'Hist. Nat. des Corall. 1756, p. 51, pi. XX. fig. A). Nordmann (Observ. sur la Faune Pontique, 1840, p. 679, pi. III. fig. 4) has described and figured them with much accuracy. In Cel- laria avicularis, Bicellaria ciliata and Flustra avicularis, they are formed like lobster's claws. In Retepora cellulosa they are pincer-like, and in Telegraphina they are articulated stings. See also Krohn in Froriep's Notizen, 1844, No. 533, p. 70. For the organs having the form of a bird's head and a lash, and which are present in certain Bry- ozoa, see also Van Beneden, Recherch. sur I'anat. &c., des Bryozoaires, in the Nouv. M^m. de Brux- elles, XVIII. 1845, p. 14, pi II. III., and Reid in the Ann. of Nat. Hist. XVI. 1845, p. 885, pi. XII. 2 Darwin''« Voyage of the Beagle, 1844, pt. I. p. 252.t With Paludicella, the muscular system is some- what different ; there are here five sets, — the 1st. 5th, 6th, and 7th of the preceding, and the parie- tal muscles. But with the 1st there is here only a single instead of a double fasciculus. — Ed. t [ § 32, note 2.] See Ilincks (Ann. Nat. Hist. Vm. 1851, p. 353), who regards these avicularia as organs of defence, and has observed them seiz- ing and retaining foreign bodies. — Ed. " ^^ 33, 34. TUE POLYPI. 43 CHAPTERS III. AND IV. NERVOUS SYSTEM AND ORGANS OF SENSE. §33. As yet only a very rudimentary and imperfectly distinguished nervous system has been made out in the Polyps ; this consists of round masses, which are regarded as composed of nervous matter (ganglia), situated in the parenchyma. A ganglion of this kind has been supposed to have been observed about the mouth. "^'^ §34. Investigations upon their organs of sense have not been more suc- cessful. However, the sense of touch appears developed over the whole surface of the body, but specially so in the extremely irritable arms and tentacles. But, as yet, no tactile nerves have been found in these parts. In the same manner, light, to which these animals show a greater or less sensibility, is perceived rather by the general surface of the body than by special organs. There are, however, in some species, at particular stages of development, during which they swim freely about, certain nicely-defined bodies situated upon the sides of the body, and which may be regarded as special organs of light and sound. This is the case with Syncoryne ;^^^ and Coryne^^^ has in their place four red organs which correspond exactly to those found on the border of the disc of the pulmograde Acalephse, and which have been re- garded as organs of sense. The organ seen at the base of the six arms of Eleutheria dlcliotoma has quite the appearance of an eye ; that is, there can be distinguished in 1 A double oesophageal ganglion has been ol> Nat. XIV. 1840, p. 22'2). Coste asserts the presence BerveJ by Dumortier (Alem. sur 1' Anat. et la of a nervous system in Pennatula (t^roriep's neue Physiol, d. Polyphrs composes d'eau douce 1836, Notizen, 1842, No. 450, p. 154). That which 5;)iar \>.il, \>\. U. fig. 2) in Lophopas cristallinus (Plu- pretended to have discovered in the foot of Act i- matelia cristata of Lamarck); and by Coste n;« (Ann. d. Mus. d'Hist. Nat. 1809, p. 443, pi. (Comp. rend. XII. 1841, p. 724)in the P/Mmao/(H (i>/««cc's Arch. 1843, p. 176) and ct-ption to this. It therefore appears singul;u- that A'd'/iAe/- (Fror(fi;)'s neue Notizen, 1843, No. 534, p. Rymer Jones {K General Outline of the Animal 81). Vail Bene.den has perceived in the canipa- King. p. 41, fig. 13), and Lesson (Dnperreij, Voy- nulate and free individuals of CampamUaria ge- age autour du Monde. Zoophytes, p. 82, No. 1, fig. latinosa and geniculata, not only eight marginal 1), expressly mention and distinctly figure these J)udies, each containing a calcareous nucleus, but openings; the first with an Actinia, the second also four nervous ganglia about the base of the with im Enmenides. According to Fan Ben edrn •stomach (M^m. sur les Campanulaires de la cote (loc. cit. p. 15) the tentacles of Campanularia yerrtilhirn, Flustra, Eschara, Cristalclla 1 This cavity which is in the arms of most Polyps and Tubulipora. *l§36, note 1.] Subsequent researches have Structure and Classillcation of Zoophytes. Phil, «hown that the cavity of the tentacles does open 1846, p. 32. — Ed. exteruully through a small papilla. See Dana, ^^37. THE POLYPI. 45 tacles have only a single row of cilia, which move regularly and volunta- rily, like the rotatory organs of the Rotatoria. By means of the currents produced by the cilia of their tentacles, many Polyps draw towards their mouth light particles of food ; ''* others make use of their ciliated arms to seize larger portions.'**' This a(;t is aided by the nettling and various prehensile organs, which are more usually found upon those Polyp-arms having no cilia. '^' These organs are found upon the tentacles of Actinia, Edwardsia, Verctillum and Alcyonium, and without doubt serve for the seizing of the prey as well as its retention until death. But these should not be confounded with special prehensile organs faumj on the tentacles of certain species. These consist of a small coriaceous capsule, from which the animal can project a kind of sting. '^"' By means of these organs, the animal can attach itself like a bur to external objects^ and not by suction, as is generally supposed. The circular or oval mouth is always situated in the centre of the an- terior extremity of the body ; it is often surrounded by a lip formed of circular fibres.''^' In a few species, the mouth projects like a cone at the base of the tentacles. <^-' Vf\i\\i\\.e Phunatellae'^^''^'' the mouth is topped by a tonguelet covered with rapidly moving cilia. Some of the Anthozoa-, which capture animals of considerable size, can, in swallowing them, dilate their mouth to an astonishing width. '^*' DIGESTIVE CAVITY OF ANTHOZOA. §37. The simple stomach of Anthozoa, which is of a variable length, opens in general directly external by means of the mouth,'" and with a few species, only, is there a muscular oesophagus.'-' With some, the stomach blends with the walls of the body,'^' but usually it is more or less isolated. There remains, therefore, a cavity of the body of variable size, and which is directly continuous with the cavities of the arms. In those Polyps living in colonies, it is prolonged into canals trav- ersing the corallum, and in this way the cavities of the bodies of all the 7 Flustra, Eschara, Tubulipora and Crista- ment is still unprojected (see his Memoir in tho tella. Nov. Act. physico-meilica XVIII. p. 300, Tab. XV. 8 Actinina. fig. 5, 9, 10). Perhaps the oreans which Erdl 9 Hydra,Coryne^Eleutheria,Se.rtularia,Cam- {Muller's Arch. 18-11, p. 424, Taf. XV. fig. 3) has panularia and Alcyonium. seen upon the tactile lobules of yeretiUum cijno~ 10 Such prehensile organs have been observed by morium a.Te of this kind. Quatrefa^es upon the clavate tentacles uf Eleu- U Actinia and Edwardsia. theria. He thinks also he has observed two mus- 'i- Hydra, Coryne. and Campanutaria. cles in their capsules, by which the retractile sting 13 Alcyonella and Cristatella. is projected (Ann. d. Sc. Nat. XVIII. 184'2, p. 276 U Actinia and Hydra. and 283, pi. VIII.; or Froriep''s neue Notizen, ^ Veretitlum, Alcyonium, Actinia ?i.rvi Hydra. 1843, No. 543, p. 230). The oval vesicles which 2 Edwardsia. See Quatrefa^es (Ann. d. Sc. Nat. roughen the tentacles of Cam panularia, and which XVIII. pi. I. flg. 2 ; pi. II. fig. 1, 2). Loven (/ri'e^/nann's Arch. 1837, 1, p. 252) has de- ^ Hydra. The stomach of the ann-polyps is not» scribed as small Spinous warts, are probably of the as has been formerly supposed, a simple e.xcavation same nature. In Hydra each hook-organ upon the in the body. It has proper walls distinct fi-om arm is surrounded by a group of similar vesicles, in those of the body, by which, however, they are the interior of which is a rigid bristle. These or- closely embraced. There is, therefore, in Hydrn gans are here found only upon the arms. They no cavity of the body, and the cavities of the ten- ure distinguished from the organs having hooks by tacles open directly into the stomach. This is also their less size, and from their having no project- true of £/f:»/Aerja (Q«a«re/ag-e«, Ann. d. Sc. Nat. ing filament. Corda has not properly distin- XVIII. p. 283). quashed them from the hook-organs, wtiose fila- 46 THE POLYPI. «^37. Polyps are placed in direct intercommunication. It is not rare to find this general cavity divided into chambers by mesenteric membranes stretch- ing longitudinally from it to the external surface of the stomach.*'" The base ©f the stomach of many, and perhaps all of the Anthozoa, is pierced by one or more valvular openings, which communicate with the cavity of the body.® These animals, by controlling at will these orifices, can allow to pass into the cavity of the body the proper materials, which are probably water and liquid chyle.® This digestive apparatus thus com- municating with the cavity of the body, reminds one of the organization of the Infusoria.*'' The cavity of the stomach is lined by very delicate ciliated epithelium, which is continuous through the orifices upon every surface of the cavity of the body and arms, and even into the intercommunicating canals of the oorallum. The color of the walls of the stomach is quite varied, and is due to cer- tain pigment cells which very probably perform the function of a liver ; for these animals are entirely wanting in any other glandular appendix of the alimentary canal, analogous to a liver.** 4 There are often eight of these longitudinal chambers, as in /'■eremach and the tubuloua cavities of the coralluni {Lister, Pliil. Trans. 1834, p. 371, and Fan Beneden, Mt'm. sur les Campanu- laires, loc. cit. p. 17). There must be direct com- munication of this kind with the Actiniae, since tliey regularly reject by their mouth nettling fila- ments, from the chambers of their body. With Hydra, the stomach conmiunicates, V>y an orifice situated at its base, with the narrow tubulous cavity of its cylindrical foot. But at the extremity of this tube there is no oval opening, and the tube itself can- not be regarded as a rectum, for it receives neither fa;ces, nor fragments of food, and is not affected by the frequent enormous dilatations of these animals from surfeit. Corda tlierefore is incorrect in as- signing an anus to these animals. (Nov. Act. phys- ico-medica XVIII. p. 302, Tab. XIV. fig. 2, E.) He appear» to have entirely neglected the foot of this animal, which, howi^ver, has been well figured by Khrenberg (Abhandl. d. Berl. Akad. 1836, p. 134, Taf II. fig. 1); and since Roesel (In.sektenbel. III. Taf. LXXVIir. and I.XXIX. lig. 2, and I,XXXVI. L.KXXV^IU. fig. 6) has jicrccived it in all unmuti- lated arm-polyps. Har.s (Faun, littoral. Norveg, p. 21) has found with a Lucernaria a stomach opening inferiorly, and communicating directly with the cavity of the body. This communication has been observed also by Frt-y and Leuckart (Beitr. p. 3) with the. 4c§ 42, 43. CHAPTER YIII. ORGANS OF SECRETION. § 42. Nothing like urinary organs have yet been found in Polyps. Perhaps the borders of the mantles of the cellular Polyps should be regarded as organs of special secretion, since by them the increase and production of these cells take place.* CHAPTER IX. ORGANS OP GENERATION. § 43. Polyps reproduce by gemmation, fissuration, and by eggs. 1. Fissuration is comparatively rare ; it takes place nearly always lon- gitudinally, and the division may or may not be complete.*^' 2. Gemmation is their most common mode of reproduction. The new individuals may be completely detached, or may remain connected with the parent corallum. a : In gemmation, complete separation of the young individual is, on the whole, rare. It is best known in Hydra, with which the buds always appear upon a certain part of the body, — that is, at its union with the foot.*^' A bud of this kind consists always of a simple fold of the wall of the stomach and the skin, so that the stomach of the young individual is in direct communication with that of the parent, and the chyme can pass freely from one to the other. When the foot of this new being has acquired a proper development, it is completely detached at its inferior extrem- ity. b : Gemmation without separation of the new beings is quite common with Polyps, and occurs with very various modifications. The buds are formed sometimes upon the sides, sometimes upon the base of the body. In the first case, the coralla have a dendroid aspect; in the second, they arc more lamelliform, spherical or lapidescent. These variations are not limited to certain genera or species, being often due to external influences, 1 The calcareous tubes of Tubipora, and tlie and Car(/o;)Ai///(a ; but, when incomi)lete, the cells corneous ones of the Sertulariiia and other liryozoa, are branched, lol)uluted, and of irrejiuiiir contour, are, without doubt, secreted by the border of the as in Agaricia, Maeandrina, and Monlicu/aria, mantle, as is true of the shells of niollusks. &c. 1 According to Roe.iel (Insektenbelust. III. p. 2. ßoe.?e/(loc. cit. III.Taf. LXXXV. fig. '2, 3, 5, Ö04, 525. Taf. LXXXIII. fig. :3\ fissuration takes Taf. LXXXVI. and LXXXVIII. fig. g. h. and Taf. jjlace transversely with Hi/iira. Longitudinal L.XX.XIX. fig. 4). The exceptions to this rule, fissuration is principally observed with the Madre- which are sometimes observed, arc probably due porina. When it is complete the cells of the coral- to lesions of au accidental nature. Iura are definitely limited, as in Astraea, Favia, ^^ 44, 45. THE POLYPI. 51 and especially the nature of the soil upon which the colony may have been fixed.=^ <■'> § 44. 3. It is probable that all Polyps reproduce by eggs. This requires two kinds of organs, one to produce the egg, the other the semen. Both kinds, ovary and testicle, have already been described in many species. Their distribution is quite varied. In some, the sexes are united in the same individual/'^ in others they are distinct/-' with the colonial polyps the sexes are separate, and each colony^^' may be composed of individuals which are androgynous, or those of one sex alone.'*' Some species are sexless, and remain so ; but they produce by gemmation individuals of a particular character, which have sexual organs.'^' These last, which have usually either a campanulate or discoid form, are separated from the corallum often before the sexual organs have been formed, and ■which they do not acquire until an advanced period of their lives. During thi.i time they swim freely about, like the pulfnograde Acalephae,*^' for ■which, as well as for young Polyps, they are often taken. '^' §45. That the relations just described really exist, may be learned from the following facts : In Coryne echinata a.nd vulgaris, there are formed at their base, quadrangular and campanulate individuals, which lay numerous eggs.'^' In like manner also, ovigerous capsules are formed about the base of Syncoryne ramosaß^ In Coryne fritillaria,^^^ the new individuals are completely detached and swim freely about, closely resembling Medusae. In this condition they are developed, and their eggs come to maturity,**' 4 According to Erdl {Froriep^s neue Notizen, 1839, No. 249, p. 101) the coralla of Veretillum cynomoTiiivi and A/ci/onium have always either male or female individuals alone. Krohn has perceived the same of Sertularia (Muller's Arch. 1843, p. 181). 5 Coryne, Syncoryiie and Campanularia. 6 Coryne and Campanularia. 7 Very striking, at least, is the resemblance of Van Benedeti's (M^m. loc. cit. pi. II.) figure of a free ftmale of Campanularia gelatinosa and those of Sam (Beskrivelser. loc. cit. p. 28, Taf. VI. fig. 14) of small Acalephae, named by him Cytaeis octopunctata, and by fVill (Horae tergestinae, 1844, p. 68, Taf. II. fig. 5) as Cytaeis polystyla. 1 R. Wagner. Isis, 1833, p. 256, Taf. XI.; also Icones zoot. Tab. XXXIV. fig. 16. - Lowen. )Viegmann\i Archiv. 1837, I. p. 321, Taf. VI. fig. 19-25. 3 Steenstriip. Ueber d. Generationswechsel, p. 20, Taf. I. fig. 41-47. 4 According to Sars (Beskrivelser. loc. cit. p. 6, Taf. I. fig. 3), these remärt-s are also true of Co- rymorpha nutans. 3 Eschara and Fliistra have a lamellated form -when fi.xed to stones, shells, or the broad leaves of Algae ; but are tubular when attached to the ^tems of plants. Alcyonella stagnorum under- ,goes similar changes in the form of its corallum. It divides in a regular dichotomous manner ■(Eichhorn, Beitr. zur Naturgesch. d. kleinsten Thiere. Taf. IV.; also Roesel, loc. cit. Taf. LXXIII. and LXXIV.), and in this form has been described under the name of Plumatella campanulata by Lawarck. But when a colony of these Polyps is fixed upon a stone or a sunken root, they com- mence to be developed in a dichotomous manner. But afterwards they become lapidescent by the liranches of both modes interlacing each other. As the mass becomes more voluminous and dense, the tubes of the dead generation support those of the living. (See Lamouroux, Exposit. method, dtg 4(>. The Campanulariae and Sertidariae produce at the end of their pedicle and branches elongated sexless individuals. But in the angles of these branches cells of another form, and containing many spherical individuals, are developed. In these last sexual organs are formed, which, in Campan- ularla genicidata, occurs without a separation of the new individuals from the coralluni, while in Campamdaria gelatinosa it is after detachment has taken place.''" § 46. In the eggs of polyps both a germinative vesicle and dot may often be seen. Frequently, however, both disappear at a very early period. The envelopes of the egg are usually of a simple,* though sometimes of a complicated structure. The spermatic particles are very active, and in some species are filamentoid, in others composed of a solid body or head, to which is appended a very delicate tail. Water does not appear to afiect either their form or motion.'-' 5 According to Krohn (MilUer^s Arch. 1843, p. 174), it is probable tliat in Cainpanularia and Ser- tularia both sexes are developed in tiiis way. From Ellis' description of Campanularia dicho- toina (Essai sur I'Hist. Nat. des Corallines, p. 116, pi. XXXVIII. fig. 3), it may be concluded that the females, mistaken by these naturalists for eggs, separate in this way from the corallum. Meyen (Nov. Act. physico-raedica. XVI. Suppl. I. 1334, II. 195, Tab. XXX. flg. 3, 4) has also taken the raedusoid females of this species for spawn. [Additional note to § 45.] The series of those polyps, the sexless (nurse-like) individuals of which produce self-dependent, medusa-like young, has been increased by several more recent re- searches. See Van Beneden, Rech, sur I'embryol. d. Tubulaires, 1844, pi. I. IV. (Tubularia and Eudendrium) ; Sars, Faun, littoral. Norveg. p. 7, Tab. I. {Podocoryna and Perigonimus) ; Du- jardin, Ann. d. Sc. Nat. IV 1845, p. 257, pi. XIV. XV. (various Hydrina). It is true that the de- velopment of the genital organs has not been ob- served in tliäse medusu-like individuals ; but they have indeed in the medusiform individuals of Si/n- coryne ramo.fa and Cori/ne/>"j7;7te?-Ja, and there- fore it may be proper to infer that the same is true of other Hydrina and Sertularina. If it is cor- rect to regard as the perfect state that in which the individuals resemble Meduste, and as the im- perfect state thit in which they are polypoid, then should we, as has been done already by many, re- move these animals from the class of the Polypi, and place them with the Acalephafi.* 1 In most Anthozoa. Eggs of this kind, belong- ing to Actinia, Coryne and Veretillum, have been figured by fVas^ner {Wiei;inann's Arch. 1835, I. Taf. III. fig. 2; Prod. Hist. Geaer. horn. at(|ue anim. Tab. I. fig. 1, and Icones zaot. Tab. XXXIV. fig. 5, 17, 23). '^ With most Bryozoa the spermatic particles are filamentous. Both from their size and their motions, they have been taken for parasites.^ KoUiker (Bjitr. zur Kennt, d. Geschlechtsverhalt. u. d. Saamtn. Flüssigkeit wirbellos. Thiere, p. 41, Taf. II. tig. 17) has s^en the spermatic particles of a thread-like form, of Fluftra carnosa, develop- ing in cells, and has seen them moving in the cav- ity of the )3ody. I have seen similar ones in'Crista-^ tella mirahilis and Pliiinate/la campaniilata.. Those which were seen by Farre (Phil. Trans. 1837, p. 403, pi. XXIII. fig. 5, g) in the cavity- of the body of Valckeria cuscuta, and were re- garded by him as intestinal worms, have an oval- body, to which is attached a delicate tail. Nord-^ mann (Pauiie Pontique loo. cit.) has found those of Cellaria avicularia having the same form. Those of Actinia have also a similar form (see Erdr Müller'/! Arch. 1842, p. 301, and Kölliker, loc. cit. p. 44, üg. 13). One should be careful and not confound the spermatic particles with the nettling organs having a similar form ; and especially as the development of these last has apparently some connection with that of the sexual organs (see Erdl loc. cit. p. 305). Accordhig to Kölliker, the spermatic particles of Alcyonidium gelatinosum have a lanceolate body, with a hair-like tail (loc. cit. fig. 11). Spermatic particles of a cercaria-form have been, observeil by fVagner (Icon. zoot. Tab. XXXIV. fig. 7, 12) with VeretiUum and Hydra ; by Fan Beneden (Rech, sur I'urganisat. d. Laguncula,. and Rech, sur I'anat. d. Bryozoaires, pi. V. in the Nouv. M6m. de Bru.'ielles, &c. XVIII.), with La- giincula ami H'ttodactylux ; by Ratliki {fVieg- mann's Arch. 1844, I. p. 161, Taf. V. fig. 6) and Sleenstriip (Untersuch, üb. das Vorkommen d. Hermaphrodit, p. 66, Taf. I. fig. 18, e) with Coryne ; finally by Kölliker (Nene Denkschr. VIII. p. 48, fig. 20, 21, 22, 24) with Pennaria, Eudendrium and Sertiilaria. In Crifiia, on the other hand, Kölliker found the spermatic particles perfectly filiform, t * [ End of additional note to § 45.] The remark- able relations here spoken of, and the conjectures as to the real zoological nature of the animals in question, have been iiretty satisfactorily cleared up by the recent researches of Agaxsiz. He has shown that the Hydroid P(jlyps are not simply a lower form of stemmed animals, producing at a given period more highly-organized Medusa;, but that they are themselves, by their structure', real Medu- SfB. See Lectures on Comparative Embryology, 1848; also Proceed. Araer. Assoc, for the Advance- ment Sc. 1849 (" On the Plan of Structure and Ho- mologies of Radiated Animals"), and Mem. Amer. Acad. loc. cit. p. 225. — Kd. t [ § 46, note 2.] I have been able to trace the- development and character of the si)ermatic par- ticles of many of the true Polyps and the Bryozoa. The developmeut occurs iu special daughter-cells, ^§ 47, 48. THE POLYPI. 53 § 47. I. With those polyps which are not sexless, and whose alimentary canal hangs free in the cavity of the hotly, the sexual organs are situated in this last. They often escape attention, since they are scarcely at all developed except at the sexual epoch. Both ovaries and testicles frequently appear as riband-like bodies, which, being attached by one extremity alone to the stomach, move freely in the general cavity of the body. Sometimes, however, they are attached longitudinally by one of their borders, like a mesentery, the opposite border being free. In other cases, again, they are attached directly to the sides of the body. The eggs and spermatic particles pass directly from the sexual organs into the cavity of the body. In Coralla having individuals of both sexes, fecundation takes place in the cavities of their bodies, which connect with each other.*'* With the others, however, the individuals of which are of one sex alone, the surrounding water is the medium of fecundation, by transporting the spermatic particles unaffected to the eggs ; and this being performed by the aqueous circulation before mentioned, impregnation takes place in the cavity of the body. § 48.* The variations of the internal genital organs in the different families are as follows : 1. With the Bryozoa, a riband-like ovary and testicle are suspended from the extremity of the stomach. In these organs are developed only two to four eggs or fasciculi of spermatic particles, from cells arranged like a string of pearls. <'' The eggs, of which the germinative vesicle and dot disappear at a very early period, are detached from the ovary before their shell is well formed, and are set in motion by the cilia of the cavity of the body. Usually they are flattened, and at first envelope,d by a thin and colorless membrane, which soon becomes thicker and darker, and has upon its borders a clear, 1 With Tendra zostericola, which is allied to Flustra, the Polyps are contained in cells closely bound to each other. But the cells of the males communicate with those of the females by an open- ing, through which the spermatic particles pass into the cavity of the body of the female (see Nordmann, Ann. d. Sc. Nat. XI. 1839, p. 191). 1 See. for Alcyonella stagnornm. Met/en (Isis, 1828, Taf. XIV. fig. 1), ioT Plumatella cristata, Dutnortier (loc. cit. pi. I. fig. 3, u, u) and for Cellaria avicularia, Nord?nann (Obs. sur la Fauue Pontique, p. 679, fig. 4, A. u).t and the particles themselves are the metamor- phosed nuclei of these cells, exactly as in other and higher animals. They have invariably, as far as I am acquainted, a cercaria-form consisting of a solid head, to which is attached a most delicate tail. The shape of this head, when studied carefully with the best powers, presents differences of zoological import. Sometimes it is pyriform (Tubularia, Actinia), sometimes conical (Astrangia), while among the Bryozoa it is long-oblong with Alcyo- ndla. I cannot therefore agree with Kolliker (Cyclop. Anat. Art. Semen. 1849, p. 497) as to the mode of development of these particles with these animals. — Ed. 5* * [§ 48.] In an emendatory note at the end of the volume, the author remarks: " Sections 2d and 3d of this paragraph should be omitted, since the genital organs, with all the Anthozoa, are attached on the internal surface of the visceral cavity. See Frey and Leuckart. Beitr. &c. p. 13." I have, however, allowed them to remain, for the sake of their notes. — Ed. t[§>48, note 1.] My own researches in 1851 have shown me that with Alcyonella the sexes are separate. The testicles and ovaries consist of pedun- culated sacs, closed at first, but which are rup- tured on the mature development of their contents. — Ed. 54 THE POLYPI. ^^ 49, 50. tvinspavenl ring. In Alcyonella and Plumatella, the eggs are of an oval shape, and of a dark-brown color. In CristateJla mirabilis, Dal. [Crista- tella mucedo, Ciiv.), they are lenticular and clear brown, and have this re- markable peculiarity : '"' Upon both sides of the encompassing ring are a number of double-pointed hooks, which, at first, are imbedded in a gela- tinous substance ; but as this last is dissolved by water, they become free, and adhere to plants and other bodies.^"' 2. With many Anthozoa, having a cavity of the body, the sexual or- gans are attached in the form of bands along the external face of the stomach. These are numerous, and during the epoch of reproduction their free borders are often plicated, and have a botryoidal aspect. This form is quite apparent in the Actiniae, where these organs are contained in sep- arate chambers of the cavity of the body,^^^ The same is true of the Ed- wardsiaeß^ With Veredllum ^'^^ and Alcyonium'-''' these organs form mesen- teric divisions which descend deep into the cavity of the body. 3. In Alcyonidium elegaris ^^' and Tuhipora musica ^''' these organs are attached to the internal surface of the cavity of the body, and have a pli- cated mesenteric forrn.'^"^ §49. The laying of the eggs takes place in different ways with those Polyps having internal sexual organs. With the Bryozoa it probably occurs through the openings near the anus.''^ With the Anthozoa, however, they pass into the stomach through its abdominal orifices, and thence are ejected through the mouth. In the viviparous Actinia, the young, devel- oped at the base of the stomach, are expelled in the same manner.'-^ §50. II. Many Anthozoa, which have no general cavity of the body, have external sexual organs. This is especially true of Hydra, where in the 2 Raspail, loc. cit. pi. Xn. fig. 10-12, pi. XIV. fig. 4-8, and pi. XV. fig. 5. 3 Turpin and Gervais, Ann. des Sc. Nat. VIT. 1837, pi. III. A. fiff. 2-4, and pi. IV. A. fig. 1-6. 4 Wagner. fViegmann's Arch. 1835, 1. Taf. III. fig. 1 ; also Icones zoot. Taf. XXXIV. fig. 22. 5 Quatrefages. Ann. d. So. Nat. loc. cit. pi. I. fig. 7, and r>l. II. fig. 10. tj Carus and Otto. Erlftuterungstafeln, Heft. IV. Taf. I. fig. 19 ; also Wagner, Icoues zoot. Taf. XXXIV. fig. 2. ^ Milne Edwards. Ann. d. Sc. Nat. loc. cit. pi. XIV. fig. 4; pi. XV. fig. 6, 8, and pi. XVI. fig. S-5. « Ibid. p. 829, pi. XII. fig. 3, pi. Xm. fig. 2, 7. 9 Rymer Jones. Outlines, loc. cit. p. 36, fig. 9, after Lamnuroux. iO KüUiker^s observation upon the sexual organs of Alcyonidium gclatinosum, Johnst. (Halo- dactyliis diaphanus of Farre), is quite remarka- ble; for he found them wanting in the isolated in- dividuals, but scattered here and there, in the form of small round sacs, in the fleshy substance of the corallum — some being ovaries, others testicles. But he is in doubt whether or not their contents are emptied into the cavity of the body or upon the outer surfaces (Beitr. loc. cit. p. 48).* 1 See, for Alcyonella stagnorum, Meyen (Isis 1828, p. 1228). '■i Rathki has often found spawn in the stom ach of Actinia (Reise Bemerk, aus Taurien, zui Morph. 1837, p. 10, and Beitr. zur vergleich. Anat. u. Physiol, in the neuesten Schrift, d. na- turf. Gesellsch. zu Danzig, 111. Hft. IV. 1842, p. 112). * 1 § 48, note 10. J With the Actinina, some of the lamellae which partition off the visceral cavity are margined each by a white, capillary, convolut- ed cord. It is attached to the lamellae by a tliin, mesentery-like membrane. These cords are the testicles. Between the spermatic lamelhie are oth- ers similarly arnuigeil, which are the ovarian, on which are situated the ovaries. With the Zoanthi- dae the relations are of the same general nature; but with the Tuhipora, Dana found six spermatic to two ovarian lamellae. See Dana, loc. cit. p. 43,. pi. XXX. fig. 3, b, c, d, e, f, and pi. LIX. fig. l,b — Ed. ^ 50. THE POLYPI. 55 same individual during the time of heat both ovaries and testicles are dcv veloped upon the external surface of the body. In the place where the eggs are to appear/^* the transparent and color- less skin rises in the form of swellings, under which the vitelline mass gradually forms. These end each in the form of an excrescence, which, being constricted at its base and rounded, has the shape of an egg. -At the point of constriction there is formed from the body of the Polyp a kind of cupel, in the cavity of which the vitellus rests by a small portion of its surface ; at this point the skin becomes thin, and ultimately appears like an arachnoid membrane enveloping the egg. In this last neither a germinative vesicle nor dot has been discovered. Its separation is preceded by a thinning of its surrounding membrane, after which the vitellus is im- mediately clothed by a gelatinous substance. In Hydra vulgaris its whole circumference is covered by obtuse p|-olongations of this kind, which, after an increase in length, divide, each once or more, at their extremity, and so present a dentated appearance. The arachnoid membrane finally bursting, the detached egg becomes fixed to some body, whilst the gelatinous coat entirely disappears. This is equally true of Hydra viridis, with the exception that here the vitelline prolongations are very short and compact. ^-^ In these same individuals testicles are developed also. Between the base of the tentacles and the place of the appearance of the egg, there are developed small conical prominences, on the apex of which is a papil- la. This has an orifice which leads into an internal cellular cavity. This is the real testicle, wherein are found spermatic particles composed of a body, or head, to which is attached a very movable tail. These particles easily escape through the orifice, and circulate in the water surrounding the Polyps filled with eggs.^'^' The number of these testicles in a single individual is not definite.'^' * 1 In the ann-polyps, gemmation always pre- 4 Warner, Icones zoot. Tab. XXXIV. fig. 10, cedes propagation by eggs. b, b. In Hydra vulgaris I have counted fifteen 2 The eggs of Hydra were long ago observed by testicles ; another individual had seven eggs and Bernhard Jussieu (Abhandl. d. schwed. Akad. eleven testicles ; and a thii'd, four eggs and twelve 1746, VIII. p. 211). But afterwards they were testicles. regarded as exanthemata of this animal (see Roe- [Additional note to § 50.] Other examples of se/, Insektenbelust. Th. III. p. 500, Taf. LXXXIII. Anthozoa having e.xternal genital organs in the fig. 1, 2). Their true nature was lately first form of egg or sperm capsules have been observed pointed out by £Arcnfterg- (Abhandl. d. Berliner by Fare Beneden. (Rech, sm Tembryog. d Tubul. Akad. 1836, p. life, Taf. II.). pi. V. VI.), Rathki {fViegviann's Arch. 1844, I. 3 The testicles of Hydra were known to the elder Taf. V.), and Sars (Favm. littoral. Norveg. p. 7, naturalists, but were taken for an eruptive disease Tab. II.), with Hydractinia, Coryne and Podo- {Trembley Abhandl. zur Geschieht, einer Polype- coryne. See also the facts collected by Frey and nart, p. 264, Taf. X. fig. 4, and Roesel, loc. cit. p. Leuckart (Beitr. &c. p. 28). These egg or 602, Taf. LXXXIII. fig. 4). Latterly this same sperm capsules may, moreover, be regarded as error has been continued {Laurent in Froriep''s imperfect male or female individuals, and then the neuen Notizen, 1842, No. 513, p. 104). To Ehren- porters of these capsules may be considered, being ierg- is due the first description of their true nature sexless individuals like those mentioned in § 45, Olettheil. aus den Verhandl. d. Gesellsch. naturf. in the category of nurse-like generations which, af- Treuude in Berlin, 1838, p. 14). ter a more or less complete development, produce generations with sex. * 'At end of § 50.] The so-called ova, mentioned particles for their development. It is also worthy above in the text, may be justly questioned as be- of remark, in this connection, that these ova sprout ing true ova, for we know of no real ova which do from the same part of the body in which eggs are not contain a germinative vesicle. Then, again, developed. Thomson, however (Edinb. New simple oval masses of cells as they are, they would Philos. .Jour. 1847, p. 287), speaks of having ob- exactly resemble the bud-Uke eggs of Aphides, and served the granular mass contained within these the " hibernating eggs " of DaoAreJO and some of so-called eggs divide and subdivide like a proper the Rotatoria, all of which are properly gemmae, vitellus, and this while still within the capsule, and and do not require the agency of the spermatic attached to the parent animal. This does not 56 THE POLYPI. ^>^ 51, 52. §51. III. There are Polyp-colonies which contain two kinds of individuals, those which are sexless, and those having sexual organs only at certain epochs. These last are canipanulate or medusoid, and their sexual organs ■are developed in various parts of their body. In Cory fie ''' and Syncoryne,^-^ the eggs appear upon the external sur- face of the stomach, then fall into the cavity of the mantle, through the openings on the border of which they escape into the water. In the medu- soid individuals of Coryne fritillaria and Coryinorpha nutans, the sexual organs appear to be formed in the angles of the borders of the disc,*'^' and in Campanularia in the disc itself. *■ § 52. As to the embryonic developments of Polyps, it is probable that in a great number (perhaps all) there is a inetamorphosis. The development commences by the usual segmentation of the vitel- lus,^'' by which it is ultimately converted into an ovoid, contractile body ; this turns upon its longitudinal axis by means of cilia, with which it is en- tirely covered, swimming about like many Infusoria. These embryos, often developed in the mother, have sometimes been taken lor swimming eggs.'-* Afterwards they attach themselves to some body, and usually lose their cilia ; the free extremity of their body opens, allowing the escape of the Polyp, which, in the mean while, has been developed in the interior, with its arms in front. Many of the Polyps thus produced multiply by gemmation, and thus become the foundation of new Polyp-colonies.*'^' 1 Wagner (Isis 1833, Taf. XI. fig. 8). 2 Loven (IViesmann^s Archiv. 1837, I. Taf. VI. fig. 19, 20). 'i Steenstrup, Ueber d. Generationswechsel, p. 2Z, 24. 1 It is indeed singular that with Hydra the divi- sion of the vitellus takes place before the eggs are either detached frora the body, or are surrounded hy a deiitated envelope. I do not yet know at what epoch the development of the embryo commences, for I have never seen the young come forth. It is impossible for me to say whether or not these Polyps experience a metamorphosis. Pallas (Ka- rakteristik d. Thierpflanzen p. 53) has seen the jouQg Polyps come forth from the egg, but he gives no descriirtion. Laurent, also, only says that the jouiig animal escapes formed from the egg, with- out describing the embryo {Froriep'.i neue Notizen, No. 513, pi. 101). The segmentation of the vitellus has been observed by f-'an ISeneden in the eggs of Pedice/lina. Sse his Rech, sur I'anat. d. Bryo- zoaires (suite) loc. cit. XIX. p. 18, pi. II. '■i As would t>e iiilerred fr.im his description, Cav- olini (loc. oit. p. 47, 50, Taf. IV. fig. 7-10 and 13- 15) ha» observed similar embryos to those of Gor- ■gonia and Madrcpora. His descriptions of various «ggs of Hertularia leave no doubt that they also were embryos (Ibid. p. 56, 80 et seq.). Grant also has taken for eggs the contractile, ovoid embryos of Lobularia digitata, which he has seen issue from the mouth of this animal (Froriep^s Notizen 1S28, No. 440, p. 340). Meyen has well described and figured the ciliated epithelium of those of Al- cynnella stagnnrum (Isis 1828, p. 1228, Taf. XIV. fig. 4, 5). Lovin has observed the elon- gated embryos of Campanularia genie a/ata, and has taken the division of the vitellus for a sponta- neous fissuration of the embryos {IViegmami's Archiv. 1837, I. p. 260, Taf VI. fig. 13, 14). Ac- cording to Rathke, who has seen movable lenticu- lar embryos in the stomachs of Actinia, these p >lyps e.\i)erience a metamorphosis ( Heise Be- merk, aus Taurien zur Morph, p. 10, Taf. 1, fig. 12). ■1 This metamorphosis has already been observed by Cavolini (loc. cit. p. 261, Taf. VI. fig. 7) with Sertularia racemona, and more lately by Lowen (loc. cit. p. 261, Taf. VI. fig. 15-17) with Campa- nularia geniculata. There are always develojjed in the interior of the embryos of Alcyonella stag- nnrum two Polyps, even before the first have es- caped from the egg ; when the escaped embryo has become fi.\e In the disc of Aequorea violacea, seventy-four ray-like bands are spread out, and the free plicated borders of these hang beneath the inferior surface of the disc, thus permitting the free escape of the eggs and sperm into the water. <^* 3. Another group of the Discophora have at the base of their tentacles four large openings, which lead into as many cavities in the disc.^^ At the base of these cavities, which formerly were regarded as respiratory organs, the genital organs are situated in the form of plicated bands. These as four bands (testicles or ovaries) are bent either into an angle or the arc of a cir- cle, forming sometimes a star with four rays,^*^> and sometimes a four-lobed rosette. ^'^^ If these cavities increase in number, the genital organs increase in the same proportion.'*^ The border of these organs is generally pro- vided with numerous tentacles which project into the cavity.'^* In the riband- like testicles numerous small sacs are observed ; each one of these opens separately into the genital cavity, while the eggs, on the contrary, are sep- arated from the similarly-formed ovary only by a gradual constriction of the latter, (i"» 4. With the Öiphonophora, all the relations of these genital organs still require much investigation. With the Diphyidae, they consist of sacs communicatii.g with the general cavity of the body.'"' During the epoch 1 Will, Horae tergest. p. 38, Taf. I. fig. 22, 23. cit. Taf. VII. ; and Wagner, Icon. zoot. Tab. 2 Wagner, Icones. zoot. Tab. XXXIII. fig. 26, XXXIII. fig. 13. a. a. ; Will, loc. cit. Taf. II. fig. 5, 7, 8, 14, 16 ; 10 Siebold, Beiträge loc. cit. Taf. I. fig. 20, 23 -, BtomuiV/c, Manuel d'Actinol. 183 i, '*' ^XXVII. and ^»//(Aer, Beiträge loc. cit. p. 40. fig. 3 : and Sars, Beskrivelser loc. cit. Vi. > . ng. n In Diphyes and Ersaea, a sac filled with cells 12, 13. opens into the general cavity of the body, and 3 Will, loc. cit. p. 71. commuidcates beside with the stomachs and respi- ■4 Milne Edwards, Ann. d. Sc. Nat. XVI. p. 198, ratory cavities. Will (Horae tergest. p. 78, 81, PI. I. fig. 1, a. b. Taf. II. fig. 23, c.) regards this sac as a sexual 5 Gaede, Beiträge loc. cit. Taf. I. fig. 1, c. {Me- organ ; and Meyen (Nov. Act. physico-med. XVI. dusa) ; and Lesson in Duperrey, Voyage loc. cit. Suppl. 1, 1834, p. 214, Tab. XXXVI. fig. 2, h. and No. 12, 13 (Chrysaora). fig. 6, 7) asserts to have seen eggs in it. Accord- 6 Rhizostomum. ing to Philippi (Muller^s Arch. 1843, p. 63, Taf. 7 Chrysaora, Medusa, Pelagia and Aurelia. V. flg. 10, a. b.), the grape-hke clustered genital See Ehrenberg, Abhandl. d. Berl. Akad. 1835, organs, with PAi/so;.'Aora, are situated between the Taf. I. fig. 1 ; Wagner, Icon. zoot. Tab. XXXIII. prehensile organs ; the smallest containing in each fig. 1 ; and Brandt, M^m. de I'Acad. de St. Peters- lobule six to ten eggs, and the largest a granular burg, IV. PI. IX. X. With the male and the female liquid (Sperm ?). Cephea, I have found the testicles and the ovaries Hollard (Ann. d. Sc. Nat. III. IS*.*! ■^ IhX PI. disposed exactly as with the Medasi'' IV. bis. fig. 33, 34) has found botryoiua. jiaases of S In Cassjo;)ea, these «rgansareeigntln number, ovaries at th' base of the tubuliforra tentacles 8 Medusa and Pelag a; see Ehrenberg, loc. (stomachs), üan ^.Oc. Jit. p. 37, PI. V.) haa also 72 THE ACALEPHAE. ^70. of procreation, the females of some Discophora are easily distinguished from the males by the numerous pouches of their tentacles, and in which -eggs and newly -hatched young are carried for a short time/^'' §70. As yet, the development of a few only of the Acalephae has been traced. It is attended by a remarkable metamorphosis. After the usual segmentation of the vitellus, ovoid embryos resembling infusoria are developed ; these turn freely on their axis, and swim about in the water by means of ciliated epithelium.'^* Shoi-tly after, they become attached by the anterior extremity to some object. Upon the opposite free extremity tentacles appear, and between them the mouth. The animal has then the form of a Polyp. ^-^ It is during this period that the young ani- mal reproduces by gemmation,'^^^ and sometimes by ix&ns,veT^Q fissuratioii. This last mode occurs in the following remarkable manner : The polyp-like animal increases in length, and its body divides trans- versely into many segments. Around each of these segments eight bifid processes are developed ; after this, each segment is successively separated from before to behind, and they float about for a time as eight-rayed Aca- lephae, but soon attain, however, their adult condition.'^ ■seen genital organs of the same form between th"; tentacles of A^almopsis ; but he found at the same time (loc. cit. p. 38, 43), in the campanuliform individ- uals produced from buds, testicles with Agalmopsis, -and ovaries with Diphyes. It may therefore be justly supposed that these various Siphonophora are compound, sexless individuals, which, lilie the Hydrina and Sertularina, reproduce by alternation of generation, — that is, by buds, — individuals having sex. l'^ Medusa aurita and Cyanea capil/ata ; see Ehrenberg, Abhandl. &c. loc. cit. Taf. III. fig. 1, 2, Taf. VIII. fig. 1 ; also, Sars in WiegmanrVs Arch. 1841, I. p. 19. 1 The development and metamorphosis of Me- dusa aurita ?i\v\ of Cyanea capiLlata have been observed by Siebnld (Beiträge lue. cit. p. 21, Taf. I. II. ; and Froriep's neue Not. No. 166, 1838, p. 177) i and by Sars {fViegmann''s Arch. 1841, I. p. 19, Taf. I.-IV.). In the first stage of development Asteracanthion, Solaster. for by this way alone can correct views be ob- 7 Asteracanthion, Oreaster, So/aster, ifC. tained upon many enigmatical bodies of this kind 8 See the figure by Sharpey, Cyclop. Anat. and seen by the naturalist. Phys. loc. cit. p. 31, fig. 8, 9 ; and Meckel's vet- For the calcereous corpuscles imbedded in the gleich. Anat. II. Abth. 1, p. 19. skin of the Holothurinae, see Koren in Froriep\s a Pentacrinus. neue Not. XX.W. p. 18, fig. 6-9 ; and in the Arch, skaudin. Beitr. f. Naturg. I. p. 449. 7# 78 THE ECHINODERMATA. ^»^^ 73, 74. ventral surface of the arms and pinnulae, a furrow, over which the soft ekin. [perisoma) passes in a bridge-like manner. '^"^ §73. In many Echino'idea the buccal cavity is provided with processes point- ing perpendicularly into the interior of the shell, and which are the points of attachment of the masticatoi'y muscles and ligaments. This osseous circle is most developed in the Echinidae.^^* and is com- posed of five processes. Between each of these is a smaller one, corre- sponding to as many ambulacral ones, each of which is perforated by a large opening.® In the Clypeastridae. there are five simple processes only ;'^' and in the Spatangidae they are wholly absent. The sub-cutaneous osseous ring about the oesophagus, in the Holothuri- oi'dea, corresponds probably to this circle. Usually composed of ten pieces, it may be regarded as a rudimentary internal skeleton, for it is the point of attachment of both muscles and tentacles. In Holothuria tubulosa its anterior border is denticulated;'*^ and in Synapta it is composed of twelve pieces, five of which have oval openings for the free passage of the aquiferous canals. '^^ §74. The general envelope of many Asteroidea is more or less covered with Tarious calcareous productions. These have the forms of lamellae, knobs, callosities, granules, immovable rays . both sharp and blunt, rough and smooth movable points, double hooks, &c.'^' In the Echinoi'dea, there are points of very variable size united to knobs which are scattered over the external surface of the shell. These points project through the thin skin covering this shell, having at their base a kind of capsular articulation.'-* Remarkable cutaneous organs are found in Synapta. These are small anchor-like hooks, by which these animals attach themselves to objects. Each of them is obliquely inserted under a small sub-cutaneous scale, which is perforated by a canal.'''* lO'In the Crinoidea, as well as in the Echino- bristled points, project from the surface of So- derms generally, the parts of the skeleton have a laster and Chaetaster. With Ophiocoma and calcareous, reticulated structure ; see Mii/ter's Ophiomastix, the margins of the arms are covered Arch. 1837, p. 93, and Ueher d. Bau. d. Pentacri- with smooth points, which in Ophiothrix are nus caput Medusae, in the Abhandl. d. Berl. Akad. spinous. In Ophionyx these spinous points have 1841, Taf. I. tig. 3. movable double hooks ; see the beautiful figures 1 Echinus, Cidaris. of Müller and Troschel (System d. Asteriden). 2 Valentin, Monogr. Inc. cit. PI. IT. fig. 15. ^ The spines of the Echino'idea have, over their ^ Agassiz, Monogr. d'Echinodermes, 21e Livr. whole extent, numerous, denticulated ribs; see containing the Scntellal, PI. XIII. fig. 3, I'l. Valentin, Monogr. loc. cit. PI. III. fig. '26. In XX.VII. fig. 7 {Lobupkora and Echinocyamiis). iSpataii^us the spines are spatulate, and in the * Tiedemann, \\vAt. d. Röhrenholothurie, &c., ("lypeastridae {Mellita, Encope, La^anum) they p. 26, Taf. II. tig. 5; also Wag'ner, Icon. zoot. are clavate. The minute researches of Valentin Tab. XXXII. tig. 15. (Monogr. loc. cit. p. 24, PI. Ill) have shown the Koren has obsorved that the osseous ring is structure of the spines of the EcliinoKlea to be very composed of ten jjieces witli Thyone fiiscus and complex. Cuvieria sr/iiamata of the Ilolothurinae. '■i The burr-like roughness of the skin of Synapta 5 (^uatrefai^es, Ann. d. So. Nat. XVII. 1842, has already been observed by Eschscholtz (Zool. p. 47, PI. IV. tig. 5 ; PI. v. fig. 7, c. c. Atlas, lift. 2, 1829, p. 12). Jaei;er (De Ilolothu- 1 With Oreaster and Culcita, the whole body is riis dissertatio, 1833, Tab. I. fig. 3) first figured covered with knobs and granulations. With Ax- the cutaneous books of Äy/ifl^j^a ßf.?e/i7. Quatre- tropecten and Utellaster, you lind flattened points Jngen (Aim d. Sc. Nat. XVII. p. 33, I'l. III.) has «ud marginal lamellae, innumerable rays, with given a very exact description of those of Synapta §^ 75, 76. THE ECHINODERMATA. 79 § 75. A peculiar calcareous plate (the madreporic plate) is observed upon the <5utaneous skeleton of the Asteroidea and Echinoi'dea. In the last it is always situated in the centre of the dorsal surface, but in the first its position varies. In the proper Asteroidae there are often several, having an excentric dorsal situation ; while in the Ophiuridae^^* it is found upon the ventral surface, and especially in the angle formed by the junction of the two arms with the tortuous mouth. In some Asteroidae a membra- nous sac (stony canal), filled with organized calcareous particles, is attached to this plate ; in others, an articulated calcareous cord stretches obliquely across the body towards the border of the mouth. The use of these parts is not yet positively known. ^-^ CHAPTER II. MUSCULAR SYSTEM AND ORGANS OF LOCOMOTION. §76. In the Echinoderms the muscular system is well developed. Its primi- tive fibres are flat, and without transverse striae.*'* In the ventral surface, and between each joint of the arms and pin- nulae of the Crinoidea, there are one or two small muscles, antagonistic to which, upon the opposite surface, is an interarticular elastic tissue.'-* In the Asteroidea, the interarticular lacunae of the internal skeleton are filled with muscles. '^"' The skin of these animals does not aid the motions of the arms, except by its elasticity. But in the Echinidae the skin Duvernaea. The similar hooks found in the sea- 1834, p. 580) has shown that they do not contain or- mud of Vera Cruz have been taken by Ehrenherg dinary calcareous matter, but rather that which is for stony concretions belonging to a sponge, and organized and perforated iii a reticulated manner, figured and named SpongoUthis anchora (Ab- A calcareous cord of a special structure is found la hand. d. Berl. Akad. 1841, p. 32-3, Taf. III. No. Asteracanthion ; see Siebold, Mullar^s Arch. VII. fig. 36). He has also taken the perforated 1836, p. 291, -Taf. X. fig. 14-18 ; and Sharpey, supports of these hooks for an Infusorium with a Cyclop. Anat. &c. loc. cit. II. p. 85, fig. 12, 13, s.* siliceous carapace, described as Dictyocha splen- 1 According to Wagner (Muller's Arch. 1835, dens (Ibid. fig. 35). But, more lately, he has p. 319), the Echinoderms do not have transversely parceived their true nature (Ibid. p. 407, 44;3). striated muscles. This has been confirmed by The discovery of analogous cutaneous organs in the Müller (Abhand. d. Berl. Akad. loc. cit. p. 214, Taf. inarl near Streitberg, by Count Münster (Beitr. IV. fig. 9) in the genera, Pentacrinus and Coma- z. Petrefak. Hft. VI. 1843, p. 92, 96, Taf. IV. fig. tula. For my own part, I have failed to perceive .9), is very interesting, since it shows the antedilu- them in Echinus, Asterias, Ophiurus, Uolothu- vian existence of Synapta. ria, and Sipunculus. yalentin (Monogr. loc. cit. Beside the cutaneous corpuscles of carbonate of ' p. 101, PI. VIII. fig. 153-155) asserts to have lime, Quatrefages (loc. cit. p. 36, PI. III. fig. 15) seen striae upon the fibres of the masticatory, spin- has found others which are of a spherical form in ous and anal muscles of Echinus ; and Quatre- the skin of Synapta Duvernaea ; and, as they fages (Ann. de. Sc. Nat. loc. cit. p. 43, PI. UX have protractile filaments, he compares them to fig. 17) has observed transverse wrinkles during the nettling organs. contraction of the longitudinal muscles of Synapta. 1 Astrophyton. 2 Müller, Abhand. d. Berl. Akad. loc. cit. p. 214, 2 These parts are found in Astropecten. Ac- 220, Taf. II. fig. 8, 12. cording to Tiedeinann (loc. cit. p. 54), they furnish S The interarticular muscular layer of the the necessary calcareous matter tor the skeleton of Asteroidae has been accurately described by the Asteroidae. But Ehrenberg (^Muller's Arch. Meckel (System d. vergleich. Anat. III. p. 14). * [ § 75, note 2.] See, for further details on this stone-canal with the Ophiuridae, Müller, Arch. I860, p. 122. — Ed. 80 THE ECHINODERMATA. § IT. covering the shell has distinct muscular bands for the motions of the points. <*> In the Holothurioi'dea and Sipunculoi'dea there is a very thick sub- cutaneous muscular layer. This is itself composed of two layers, — the first and upper being made up of circular, the second and lower of longitudi- nal fibres. In the Holothurioi'dea,^'* these fibres form five large, thick, ■widely-spread bundles, which are inserted into the osseous ring. In the Sipunculoi'dea, these bundles are more numerous, but more compactly bound together. ^^' The muscles of mastication, of the digestive canal, and of the tentacles, ■will be treated hereafter. § 77. With the exception of the Synaptinae and Sipunculoi'dea, the Echinoderm» have special, tentacular, locomotive organs (ambulacra). These are hollow and very contractile prolongations of the skin, and communicate througk the ambulacral pores with small contractile sacs (ambulacral vesicles), found upon the internal surface of the coriaceous or calcareous envelope of the body. The ambulacra and their vesicles have transverse, longitudinal fibres,, and contain a clear liquid, which, from contractions, oscillates from one tO' the other through the pores. In this way the ambulacra are capable of erection and elongation, and the animal uses them as feelers to find a proper object of attachment ; and on this account, also, they have in some species a suctorial extremity. These oi^ans, which are sometimes locomotive, sometimes prehensile, have the following variations of structure and form : I. With the Crino'i'dea they are small, delicate and cylindrical, and are found upon the borders of a furrow, which runs from the mouth along the soft perisoma covering the arms and pinnulae. Each one of them is cov- ered with small cylindrical, clavate tentacles. ^^> II. The Ophiuridae have upon their arms, and between the plates, pores which connect with small cylindrical ambulacra ; these last, from numerous small warts, present a studded aspect.'^' III. With the Asteroidae they are situated in a double or quadruple row, in the ventral furrows which extend from the mouth to the end of the rays. They form compact cylinders of considerable size, the acute or truncated extremity of each of which has a sucker.'^* IV. With the Echino'idea they are situated upon an elongated stalk, and have a sucker. They are found both upon the ambulacral plates and immediately around the mouth. <*> Being extremely movable, they are < Valentiriy Monogr. loc. cit. p. 35, PI. III. fig. dae are attached to surrounding objects ; see 59. Erdl in IViegmann's Arch. 1842, I. p. 58, Taf. J The cutaneous muscular system of Holothuria II. fig. 1, a. has l)een described by Tiedemann (loc. cit. p. 27, 3 Beside the very correct description giv«i of Taf. II. IV.); and that of Synaptn by (^uatre- these organs by Tiedemann (loc. cit. p. 56), see- fagen (Ann. d. Sc. Nat. loc. cit. p. 41). Rymer Jonen (A Oen. Outl. of the Anira. King. 6 For the muscular system of Sipunculus nn- p. 148, fig. 65). It appears that in Astropecten dus, see Grube, ia MuUer^s Arch. 1837, p. 240, the e.\treraity of the ambulacra can be inverted,, Taf. XI. fig. 1. thus compensating for the sucker found in Echi- 1 The ambulacra of Comatula, which have ac- naxter, Aste.riscu.i, and Asteracanthion. live vermicular movements, have no oi>ening at •• With Echinus the suckers, which exactly xe- their free extremity ; see Müller, Abhand. d. Berl. semble the other ambulacra, are fixed upon thQ Akad. loc. cit. p. 222, Tab. IV. tig. 13, 14. contractile membrane surrounding the mouth. ^ By these the very active arms of the Ophiuri- With Upatansus and Ech.inanth.us there is ^ 78. THE ECniNODERMATA. 81 chiefly locomotive ; for from them numerous points are prolonged, by which they adhere to objects, and to which they become afterwards fixed by their sucker. They are covered with ciliated epithelium, and their suckers are made firm by a coarse calcareous network. Elongated cal- careous corpuscles of the same nature are found also in their walls, — some branching and others hook-like.'"'* V. With those Holothurioidea which have them, they have a more or less complete sucker, and are scattered irregularly over the entire surface of the body, or disposed in regular rows. Usually very short, they ca.n be retracted deeply in the skin ; but they are capable of equal prolongation, and thus perform well the function of suckers. *"> The ambulacral vesicles, which are intimately connected with the circu- latory and respiratory systems, will be fully treated hereafter. • §T8. With the Echinoidea, and Asteroidae, there are other movable organs (pedicellariae), which, scattered over the surface of the body, are prehen- sile, and used in a pincer-like manner. With the Asteroidae, they usually consist of two delicate forceps-like pieces (pedicellariae forcipatae), or of two large valvular flaps (pedicellariae valvulatae). . Grenerally they are not pediculated.'^' Those of the Echinoidea have been caret'ally studied in Echinus. They are numerous, and occur for the most part about the mouth, presenting three dili'erent forms: 1. Those composed of three short, lenticular pieces (pedicellariae gennniformes). 2. Those formed of three long delicate pieces, laterally denticulated (pedicellariae tridactyli). 3. Those with three laterally denticulated spoon-like pieces (pedicellariae ophiocephali). They are supported by a base of calcareous, reticulated substance; and in the Eohinoidea, always rest upon a stalk, the lower part of which contains a cylindrical, calcareous nucleus, while the remaining portion is soft, and capable of a spiral contraction.'-* Here also they are covered with ciliated epithelium, and can, by means of movable processes, seize hold of objects, which, being passed along, may be conveyed even from the dorsal surface to the mouth. near the mouth, and opposite the ambulacral Astrog-onium, they are valvular and without a rosette, a row of ambulacra having special p ires. pedicle ; see Müller and Troschel, loc. cit. p. 5 See yalentin, Mouogr. loc. cit. p. 37, PI. IV. 10, Taf. VI. fig. 3-6. v., and Erdl in fViegmann's Arch. 18-1'2, I. p. - The pedicellariae of Echinus were, at first, 55, Taf. II. fig. 10. The corpuscles found by taken for parasitic Polypi by O. F. Müller (Zool. Ehrenberg (Ahhandl. d. Berl. Akad. 1841, p. 324, Dan. I. 1777, p. 16, Tab. XVI.). See Lrimarck, Taf. III. No. VII. fig. 37, a. b.) in the marine Hist. Nat. des Anim. sans Vert(5bres, II. p. 75. sand of Vera Cruz, and figured under the name More recently, Agassiz (l-'^alentin's Monogr. loc. of Spongolithis uncinata, are only the cruciform cit. p. 5]) has expressed the opinion that they were parts of the skeleton of Echinus. This will be young uidividuals. The researches of £)eWe Chiaje evident from comparing them with the calcareous (Memor. sulla storia e notom. degli Auim. senza. corpuscles flgui-ed by Valentin (Monogr. loc. cit. Vertebr. II. 1823, p. 324, Tab. XXIII.) and of PI. V. fig. 65). Sars (Beskrivelser, &c., p. 42, Tab. IX.) upon 6 Catalogue of the Physiol, series of Comp. Echinus, Cidaris, and Spatangus, have dispelled Anat. contained in the Royal Coll. of Surgeons, all doubts as to the real nature of these organs. London, IV. 18.38, p. 196, PI. XLIX. fig. 3-5. Very correct descriptions of them have lately been 1 With Z/Miparatns, and with Coma- sima, which, having made its escape by the loss tula, where Müller (Al)handl. d. Berl. Akad. of an arm, looked with scornful eyes upon its per- 1841, \>. 233) has found tluiii in the anus, they «ecutor, is pleasant to read, but is far fi-om set- extend jirolialily through the intestine. tling this (juestion. 1 MuHer, Abhaudl. d. Berl. Akad. 1841, p. 222, 1 Asteroidea, EchinoHdea, and Sipunculoldea. •^ 84. THE ECIIINODERMATA. 85 •which, by their contraction, is pressed into the cavity of the tentacles for lubrication/-' The retraction of the tentacles is clue in part to their own contractility, and in part to the numerous muscles, which, arising from the internal sur- face of the cavity of the body, are inserted into the osseous circle. By these means, it, together with the tentacles, can be retracted into the body.'''' With the Sipunculidae the tentacular apparatus consists of a fringed border on the margin of the mouth, which is also provided with vesicles.'''' In Sipu/iciilus, and Phascoloso/7ia, there are four long muscles, which, arising from the internal surface of the body, pass on to the mouth, and are retractors of the tentacular membrane. '■"' It is possible that these oral tentacles serve not only as prehensile organs of food, but also as those of locomotion and respiration.'''* § 84. The mo7dh of the Comatulinae presents nothing remarkable ; but with the Asteroidae, it is covered with hard papillie, projecting from its corners and angles. In the Ophiuridje, the inverted angles are covered with hard papillfe, while the everted ones have calcareous teeth, between which are concealed soft cylindrical tentacles. Immediately behind all of these, the entrance of the stomach is indicated by a membranous spKincter. In the Asteroidae, however, this is wanting, there being a short oesophagus leading directly into the stomach. With the Echinoidea, and Holothurioidea, the mouth has a soft circular lip, between which, with the Echinidae, and with the Clypeastridae, pro- ject the points of enamelled teeth. The mouth of the Echinidae, and Clypeastridae, has a very remarkable masticatory apparatus. In the first, the calcareous basis which supports the teeth has long been known as AristotWs lantern. This conical basis is divided into a base and summit ; the first being the superior part of the animal itself, while the second is formed by points of teeth projecting from the mouth. It is, moreover, composed of fifteen pieces, five of which are three-sided, hollow pyramids, and so adjusted that they touch each other by their plane surfaces, presenting externally the third surface which is convex. This last has internally a longitudinal furrow, in which is fitted a very long, narrow and slightly-curved tooth. Beside these five principal pieces, which form the jaws of Echinus, there are two other kinds, much 2 These vesicles are found in Holothv.ria and 3 In Pentacta, there are five large cylindrical Chirodola ; see Tiedemann, loc. cit. Tab. II. fig. muscles arising from the subcutaneous longitudinal 4, e. 6, i. ; also the Catalogue of the Museum, Lon- ones, and inserted into the osseous circle ; — they don, &c., IV. PI. XLIX. fig. 1, 2 {Holothuria tuba- are special retractors of the tentacles ; see jl/ec^e/, ' losa) ; and the Atlas Zool. du Voyage de 1' Astrolabe. System d. vergleich, Anat. IV. p. 62. Zoophytes, PI. VIII. fig. 3 (Ckirodota fusca). * I am inclined to regard as tentacular the two In Pe/iZacfa do/jo/u?n, I have found only a single vesicles of Poll, in Sipunculus ; and of which cylindrical vesicle fixed to the circle of tentacles. Delle Chiaje (Memor. &c. Tav. I. fig. 6, d.) per- In Synapta Duvernaea {Quatrefages Ann. d. ceived only one, although Grube {Midler's Arch. Sc. Nat. loc. cit.), these vesicles are entirely want- 1837, p. 251, Taf. XI. fig. 2, P.) has seen them ing. both fixed in a space circumscribed by the tentac- Cuvier (Anat. Comp. V. p. 454) and other anat- ular membrane, omists (see Grant, Outlines, &c., p. 333) hava 5 Grxoc, Ibid, p. 241, Taf. XI. fig. 1, u. 2, m. m.; erroneously taken these parts for salivary organs, and Delle Chiaje, Memor. &c. Tav. I. fig. 3. They do not communicate with the digestive canal, 6 The oral tentacles of Synapta Duvernaea, but connect freely with the circulatory and respir- which, according to Quatrefages (loc. cit. p. 63, atory systems, — a point, therefore, to which we PI. IV. fig. 1), have suckers on their internal sur- shall further allude hereafter. face, are certainly used as locomotive organs. 8 86 THE ECHINODERMÄTA. •§. 85, smaller. Of these, five are elongated quadrilateral plates, placed at the base of the lantern, between each two pyramids. The other five, smaller and longer, are curved upon the first. All these pieces are united by many tendons and muscles to each other, and to the neighboring osseous circle which projects inwards from the shell. The muscles of mastication are in ten pairs ; five of these arise from the longest processes of the osseous circle, and are inserted on the pyramids below the summit of the lantern. The other five, on the other hand, pass from the shortest processes of this circle to the base of the pyramids. By this arrangement, when the first five contract and separate the sum- mits of the pyramids together with their teeth, the second five, contracting also, carry the points of the teeth again together, by separating the bases of the pyramids. ^^^ In the Clypeastridae, the masticatory apparatus is more simple. It is composed of ten unequal, triangular pieces, joined together, V-form, two and two. Each of these pieces has in its projecting angle, a furrow in; which a tooth is fitted. These five jaws are so ai-ranged around the mouth that their angles and the points of their teeth meet together in its centre. ^^* § 85. The digestive cavity of the Ophiuridae is only a simple stomachal sac, occupying the centre of the hollow disc of their body. It is divided by walls projecting inwardly, into many caeca, which never extend into the rays.^'^ There are usually ten of these caeca, which in Astrophyton are subdivided into numerous smaller caeca. ^^^ With the Asteroidae, the stomach is large and has a similar situation ; but it sends ofi" radial caeca into the rays. In those species which have an anus, the digestive canal may be divided into three parts. The stomach is separated into two chambers by a circu- lar, projecting fold. The first of these is the true stomach, and the second sends oiF the radial caeca. A narrow, short rectum, passing off from the stomach, forms the third part of this canal, and terminates in an anus, situated upon the back of the animal and concealed among points, callosities, &c. This rectum has folds which, of a variable length and some- times branched, are called the inter-radial caeca, and are situated between instead of in the rays.'''^ . In the Comatulinae, this canal consists of a coecum situated at the end of a short oesophagus, and which, after a spiral course about the axis of the body, terminates in an anus having the form of a short tube projecting from the ventral surface not far from the mouth. <^^ In Comatula europaea, the axis, around which the digestive canal passes 1 This apparatus has been minutely descrilted by 2 Meckel, Syst. d. vergleich, Anat. TV. p. 60. Tiedemann (loc. cit. p. 72, Taf. X. fig. 1, 2), by 3 See also Tiedernnnn Qoc. cit. Taf. VII.), whose Meckel (Syst. d. vergleich, Anat. IV. p. 56), and beautiful figures have been copied everywhere ; by Falentin (Monogr. &c. p. 63, PI. V.). See and the original designs of the digestive cavity of also the beautiful figure by Rymer Jones (Om^ Asteracanthion, Archaster, AwACulcita^hy Miil- lineof the Aniin. King. &o. p. 167, fig. 70, 71). ler and Troschel (loc. cit. Taf. XI. XII.). 2 A^assiz, Monogr. &c. 2" Livr. Scutelles. p. < Upon the digestive canal of Coinatulct, see 15, PI. XII. XIII. XIV. &c. Heusinger, Zeitschr. f. d. organische Physik. UI. I Konrad, De Asteriaruni f.ibrica, fig. 5. 1829, p. 3rl, Taf. X. XI. § 86. THE ECHINODERMATA. 8T spirally, consists of a spongy substance, from which projects a lamina like the lamina spiralis of the conch of a snail shell/^' In Spatangus, the toothless mouth opens into a delicate oesophagus which passes insensibly into a long tube of nearly the same size. This last makes two convolutions in its course, and sends off at about its anterior fourth a very long caecum. The digestive canal, situated between the origin of this caecum and the oesophagus, is of a dark color and has transverse plicae, while the remaining portion below is smooth and of an orange hue.*"^ In the Clypeastridae, the numerous spiral turns of this canal are sup- ported by many calcareous laminge situated upon the interior of the shell. ^'* In many species of Clypeaster, this canal has at its commencement, transverse folds, and further on numerous lateral caeca, which are sepa- rated from each other by laminas like those just described.''*' In the Echinidae the pharyngs has very thick muscular walls, and is surrounded by masticatory organs. Upon it succeeds a proper oesophagus, which, after a few convolutions, passes to the anus situated in the centre of the back. The digestive canal is a caecum given off by this last, and has many spiral turns in the cavity of the body.'^' In the Holothurioi'dea, the very muscular pharynx is surrounded by the osseous circle. In the Holothurinae, the intestinal canal, which is long and equal throughout, has many turns from behind forwards, ending at last in a large cloaca situated at the posterior part of the body. But in the Synaptinae, it is short and nearly straight, and terminates in an anus having no cloaca.*^"' In the Echiuridae ^^' this canal closely resembles that of the Synaptinae. In the Sipunculidae it is long, making its first turn about the middle of the body, and its second near the posterior extremity. The ascending and descending portions of this last pass spirally around each other ou their way to the anus which is situated on the ventral surface of the body.^^'> § 86. As to the glandular appendages of the alimentary canal, the salivary orga?is are perhaps entirely wanting in these animals. In the Holothurinae alone, are there particular appendages opening into its anterior portion, which could be regarded as organs of this nature. In the different genera, species, and even individuals of this family, these appendages widely vary as to form and number. 5 Müller, Abhandl. d. Berl. Akad. ISil, p. 230, loc. cit. ; afterwards by Quay and Gaimard (At- Taf. V. las zool. du Voyage de 1' Astrolabe. Zoophytes, PI. 6 See Merkel, Syst. d. vergleich, Anat. IV. p. VI. fig. 2, PI. VII. fig. 3). The cloaca is always 65, a.T.d Delle Chiaje, Mevaor. &c. Tav. XXV. wholly attached to the skin by numerous tendinous fig. 12 ; also Carus and Otto, Erläuterungstafeln fibres. In Chirodota fusca the intestine is spiral z. vergleich. Anat. Hft. IV. Tab. I. fig. 25, and (Atlas zool. &c. PI. VIII. fig. 3) ; but in Synapta Wagner, Icon. zoot. Tab. XXXII. fig. 8. The Duvernaea it is nearly straight (^Quatre/aifes natui'e of the canal figured by Delle Chiaje is yet Ann. d. Sc. Nat. loc. cit. PI. II.). unknown. Ic arises from the first portion of the U See the remarks of Forbes and Goodsir upon intestine, and returns to it at its middle portion, the Anatomy of Thalassema and Echiurux (Ji'ro- It has not been mentioned by Meckel. riep's neue Notizen, No. 392, p. 273, fig. 12). 7 Agassiz, Monogr. des ScuteUes, p. 1-1, PI. IH 1- The alimentary canal of Sipunculus nudus, fig. 19, a. and of Ecliinorhyncus, has been faithfully de- 8 Ibid. p. 17, PI. XXII. fig. 28 (Laganum and scribed by Delle Chiaje (Memor. &c. I. p. 9, Tav. Melitta). I. fig. 5, 6 ; p. 126, Tav. X. fig. 11) and Grube 9 See Tiedemann and Valentin, loc. cit. {MiUler^s Arch. 1837, p. 245, Taf. XI.). I have 10 The digestive canal of the Holothurinae was found a similar intestine in Phascolosoma granu- first figured by Delle Chiaje and by Tiedemann, latum. ^8 THE ECHINODERMATA. ^ 86. In Hohthuria tuhulosa, they are cylindrical, pure white, and very nume- rous, being united in bundles which are attached to the digestive canal near the pharynx by short white pedicles."* In Fentacta doliohim, there is usually only one of these organs, — a small, white, curved horn, which sends to the pharynx a very tortuous canal, which is widely removed from the excretory duct of the genital organs. The whiteness of these organs in Holothurinae is due to a reticulated calcareous skeleton in their walls.*-* The radial caeca of the Asteroidae ought probably to be regarded as hepatic organs. They are often quite developed, extending as a double canal from the stomach into each ray. Their walls hav.e numerous small botryoidal vesicles, which secrete a yellow liquid, usually each of these ten liver-like organs arises from the stomach by a proper canal ; *^' but in some, two of them connect with this organ by a single canal.*** With those Asteroidae which have an anus, there is another series of glandular appendages, the inter-radial caeca, which pass oif from the rectum. Their function is not yet known. They contain a brownish liquid, in which, with Aster acanihion ruhens, no uric acid has been found. In Astrogonium, Solaster, and Asteracanthioji, these organs are branched, and only two in number.® In Archaster, and Culcita, there are five ; but in Cidcita cori- acea, each of these is divided dichotomously into two other long botryoidal caeca, which, separated by a septum, are spread out between the rays.'"* In Astrojjecten,'''' which is without an anus, there are sometimes found two short, analogous caeca, which open into the base of the stomach by a com- mon orifice. But in Luidia, which is also without an anus, these organs are entirely absent.*'^* In the other Echinoderms, which are entirely without these glandular appendages, the walls of the alimentary canal probably secrete the fluid requisite for digestion, and thus supply also the want of the hepatic 1 It has already been shown that the cyliiidrical Tiedemann (loc. cit. Taf. VII. or, Wasner, Icon, vesicles of Hotoihuria taken by Citvier and other zoot. Tab. XXXIl. tig. 1). It is the same, also, in naturalists for salivary orj,'an3 do not communicate Archaster, Culcita, and Luidia ; see MuUer and with the digestive canal-, but rather with the tenta- Troscliel, loc. cit. p. 132, Taf. XI. fig. 2 ; Taf. <;les. The white appendages of Holothuria tuba- XII. fig. 1. losa were first described as testicles by Delle 4 Asteracanthion ; see Konrad, De Asteria- Chiaje (.Memor. &c. I. p. 97,Tav. Vlll. fig. 1. c), rum fabrica, fig. 1 ; and Müller and Trosckel, and Tndiiiiann (loc. cit. p. 29, Taf. II. fig. 6, loc. cit. Taf. XI. fig. 2. p.) as-i-iM ,1 t i tliem the same function. It is cer- S See Müller and Troschel, loc. cit. p. 132, Taf. tain that Uir\ li;ive no testicular character, although XI. fig. 1 {Asteracanthion rubetis); an entire I cannot ailirni that they are salivary organs, group of these rectal coeca of Asteracanthion They have been figured, in Holothuria atra, by glacialis, has been figured by Konrad, loc. cit. Jaeger in his dissertation : De. Hülothurüs, Tab. fig. 1, d. III. fig. 2, e. e. « Müller and Troschel, loc. cit. p. 132, Taf. XI. Ü Tliis calcareous tissue has been observed by fig. 2, Taf. XII. fig. 1. Jaeger (U,c. cit. p. 38, Tab. III. fig. 7), by fVag- ? Tiedemann, loc. cit. Taf. Vn. ner(Froriep\i neue Not. No. 249, 1839, p. 99), 8 Müller and Troschel, loc. cit. p. 132. and by ATro/m (Ibid. No. .356, 1841, p. 53). This 9 According to Valentin's figure of the inti- last oJ-server, who uflirms that these organs are in mate structure of the digestive membranes of Kchi- connectio.; with the great circulatory vessel sur- nns, they are lined with hepatic epithelium, lilco rounding the digestive canal, compares them to the that of the Lunibricinae, and tliat of the I'olyjis, stony canal of the Asteroidae. already mentioned (Monogr. &c. PI. VII. fig- 126, 3 In Astropecten aurantiacus, according to 131, 133). ■^ 87j 88. THE ECHINODERMATA. 89 CHAPTER VI. CIRCULATORY SYSTEM. §87. The vascular, sanguineous system of these animals is yet mperfectly known. The constant confusion and imperfection of its descriptions are probably due to the fact that it has not been carefully distinguished from the respiratory system ; and also, as was true of the Acalcphae, because it has been confounded with the aquiferous system, which is usually pres- ent. From all the old and new researches upon this subject, it is evident that all the Echinoderms have an isolated system of this kind, composed usually of both an arterial and venous trunk, between which there is, in some spe- cies, an organ like a heart. §88. In the Crinoidea, there is, at the base of the calyx, a heart-like saccu- lus, from which pass off vessels into the central cavity of the arms, the cirri, and the pedicle when it is present. From its centre, another vessel is given off for the spongy axis of the cavity of the body.^'^ The Asteroidae have three vascular rings, one of which is under the skin of the back, while the other two are beneath, around the mouth. Between these vascular rings there is a long muscular heart, which, united to the calcareous pouch or cord, extends from the madreporal plate to the mouth. It is probable tliat the Asteroidae, which have many of these plates, have also many calcareous cords and hearts.^-' From these vascular rings numerous other vessels are sent off, some to the stomach and its appen- dages, and the genital organs, and others to the ambulacra and their vesi- cles. '•'> 1 The extended, and in some respects contradict- situated beneath the nervous branches of the arm, ory works of Tiedemann und Delle Chiaje {\oc. and directly above the calcareous articulations, ami cit. ; see, also, Meckel, Syst. d. vergleich. Auat. the passage of which through the arm into the V. p. 25 ; and Sharpey Cyclopsed. &c. II. p. 41) calyx Midler (loc. cit. p. 233) has not been able have not, for reasons which may be stated, cleared to clearly make out, is probably a blood-vessel. It up this point. The same may be said of what is yet unknown how the blood of these vessels is relates to the blood of these animals, for it has distributed to the organs. been confounded in part with the ambulacral Uquid 2 As in Echinaster solaris, and Ophidiaster belonging to the aquiferous system. See fVai^ner, multiforis ; see Müller and Troschel, loc. cit. Äur vergleich Physiol, der Blutes, 1S33, p. 28. p. 134. The observations of £)e//e Chiaje (Jlemor. &c. 3 According to Tiedemartn (inc. cit. p. 49, Taf. II. p. 345) and of Cams (Analekt zur Natur, u. Till.), the lower extremity of the heart of Astro- Heilkunde, 1829, p. 132, and Lehrb. d. vergleich, pecten aurantiacus opens into the vascular ring- zoot. 1834, p. 673) do not give correct ideas upon which surrounds the mouth. This last sends arte- the mode and direction of the circulation of these rial branches to the stomach, the coeca, and the animals ; for it is evident that they did not see it, genital organs ; the superior extremity of the- but only the vibratile phenomena of the aquiferous heart communicates in like manner with another system. vascular rfng upon the back, and which receives the 1 The vascular system of ComaUila and Pen- veins of the organs just mentioned. From a third tacrinus has become known through Heusinser and reddish vascular ring, situated directly under (Zeitsch. f. organisch. Physik. III. 1828, p. 373, the skin of the mouth, Tiedemann has seen pass Taf. X. XI.) and Müller (Abhandl. d.Berl. Akad. into each ray a vessel placed superficially in the 1841, p. 198, 236, Taf. V.). The membranous canal, furrow of the ambulacra, but h( did not ascertaia 8^ 90 THE ECHINODERMATA. In the Echinidae, the heart is long/^' and attached to the cesophagus. In Echinus, it has several saccular enlargements, and internally has a cavernous aspect, due to numerous irregularly arranged septa. At each of its extremities there are two vascular rings. The two below are situated on the top of the lantern and surround the oesophagus, while the two above surround the anus ; all belong probably to the arterial and venous systems. One of these last sends off five branches to the genital organs, while the other receives one of the two trunks which pass along the whole length of the intestinal canal. Two longitudinal vessels, which send oiF branches right and left, pass between each of the five pairs of ambulacral organs. These are, probably, a branchial artery and vein.^''' In the Holothurinae, the vascular system, which is without a heart, is very distinct. An aortal trunk arises from the vascular ring, which sur- rounds the oesophagus, and ramifies upon the intestine and the genital organs. By a reunion of these ramifications, a second trunk like a vena cava, is formed. This divides into two arteries, which ramify upon the branchiae, and from which arise two branchial veins, which return to the aorta. '•'' With the Sipunculidae, and Echiuridae, there is a main vascular trunk, which, after sending ofi' laterally small branches, passes along the ventral median line, above the digestive canal. '"^ Us relations with the rest of the vascular system. Moreover, he has taken for an isolated, special sanguineous system belonging to the ambulacra, the aquiferous system, which communicates directly with the ambulacra, and which forms a third ring, situated between the two sanguineous ones of the mouth. Volkmann's description (Isis 1837, p. 513) is wholly different. According to him, the vascular trunks of the superficial ring, and which are located in the furrows of the arms of Asteracan- thion violaceus, send off laterally ambulacral branches ; the oral ring, situated more deeply, sends off branches, which, passmg through the cavity of the body, go to the raiys and ambulacra, and freely communicate with the cavity of these last. This same ring has also an anas- tomotic CQpnection with that of the back. Accord- ing to this, the circulation occurs, he thinks, in the following manner : The heart sends the blood into the superficial oral ring ; thence it passes by the vessels in the furrows of the arms into the cavity of the ambulacra ; these last, »acting as venous hearts, send it, by the vessels in the interior of the rays, to the second oral ring, from which it passes to the third and dorsal ring, and thence to the heart. It is evident that Volkmann has taken a part of the aquiferous system for that of the sanguineous one ; and it is probable that he did not observe the second oral ring. No correct idea can be formed of the distribution of the arteries and veins of the Asteroidae, or of their vascular system in general, except by carefully separating it from the aquifer- ous system, and considering tlie fact that the blood- vessels do not open into the ambulacral vesicles, but probalily are spread as a capillary net-work upon their walls. 4 The heart of Echimix, which is accurately described by Valentin (Monogr. Aic. p. 92, 1*1. VIII.), is attached to the cesophagus by a kind of mesentery. 5 These details are supported by Valentin (loc. cit. p. 93), who has already added much to the labors of Tiedemann and Delle Chiaje upon the sanguineous system of Echinus, although, Uke hi* predecessors, he has been deceived as to its con- nections. The received opinions upon the circulation of these Echinoderms are, therefore, hypothetical. The nature of the live glandular organs, which Val- entin has seen communicate with one of the two vascular rings situated upon the lantern, is very problematical (Monogr. &c. p. 95, PI. YII. fig. 119, i. 120). 6 See Tiedemann, loc. cit. p. 15. The sanguine- ous system of Synapta Duvernaea, as described by Quatrefages (loc. cit. p. 58), corresponds, properly, to the aquiferous system of Holothuria., which Tiedemann also has taken for a special sanguineous system of the skin and ambulacra. Hereafter we shall notice further both of these sys- tems.* <■ For the sanguineous vascular system of 5;'/)?/ n- culus, and Echiurus, see Grube and Krohn (Müh ler's Arch. 1837, p. 248 ; 1839, p. 35U), also Forbes and Goodsir (Froriep's neue Not. No. 392, loc. cit.). The vascular trunk embraces there the nerve so closely, that care is necessary not to overlook one, or confound both together. Quatrefages has found in the anterior part of the body of Echiurus Gaertneri three heart- shaped swellings of tlie blood system, namely, a ventral heart upon the ventral vessel, a dorsal heart upon the dorsal vessel, and a mesenteric heart situated beneath the digestive tube. This last comnuinicates with the ventral heart by a flexuous vascular canal, and with the dorsal vessel by a small vascular ring ; see Ann. d. Sc. Nat. loc. cit. p. 324, I'l. VI. tig. 4. * [ § 88, note 6.] See, for the vascular system of the Holothurioidea, Müller (Arch. 1850, p. 229), who has carefully studied it with the larger Synaptinae. He confirms Tiedemann^s observa- tion above quoted as to the general distribution of the vessels, and especially as to the presence of a splanchnic system, which, as is well known, Quo- trefages has supposed to be wanting. — Ed. ^^ 89, 90. THE ECHINODERMATA. 91 CHAPTER VII. EESPIEATORY SYSTEM. §89. The respiration Df the Echinoderms is performed in various ways. These are : 1. By exclusively respiratory branchiae. 2. By organs serving at the. same time other functions. 3. By means of water passing through the openings of the skin into the cavity of the body, and aerating the blood through the capillary vessels of the viscera. With the Asteroi'dea, Synaptinae, Sipunculidae and Echiuridae, every individual has always two of these modes of respiration, and sometimes all three, as with the Echinidae and Holothurinae. § 90. I. Organs which are exclusively respiratory are found in the Echi- nidae, Holothurinae, and Echiuridae. They consist of external branchiae in the first, and internal in the last two. The external branchiae of the Echinidae are situated upon the soft membrane of the mouth, being formed of five pairs of arborescent, hollow lobules. '^^ They are contractile, but cannot be retracted within the body. They are covered both internally and externally with ciliated epithelium. The cavity of each communicates with that of the body by a large ori- fice situated on the internal surface of the oi'al membrane. ^-^ By this means they are bathed with water upon both of their surfaces. Their walls contain a coarsely reticulated calcareous skeleton,^''' and without doubt, also a capillary net-work belonging to the branchial vessels. The internal branchiae of the Holothurinae arise as two tubes from the cloaca of the intestinal canal, and send ofi", through the whole cavity of the body, numerous coecal branches. '^> In Holothuria tubulosa, one of these tubes is closely connected with the turns of the intestine, while the other is attached to the inner .walls of the body. With the first, espe- cially, may be perceived the ramifications of the branchial vessels. They are also covered with ciliated epithelium, and their contractile and expan- 1 The ramified organs of the Echinidae, already been very well described by Tiedemann (loc. cit. known by Tiedemann (loc. cit. p 78, Taf. X. fig. p. 11, Taf. II. or Wagner Icon. zoot. Tab. 5, d. d.) and Delle Chiaje (loc- cit- H- P- 338), XXXII. fig. 9), and by De/le Chiaje (loc. cit. have been more exactly described by Valentin Tav. VIII. IX.). See also Atlas Zool. du Voyage (Monogr. &c. p. 82, PI. IV. fig. 57 j PI. VIII. fig. de 1' Astrolabe. Zoophytes, PI. VII. fig. 2, 9, p. 42), and by Erdl (fViegmann^s Arch. 1842, I. {Holothuria ananas) and PI. VII. fig. 3, e (Clad- p. 59, Taf. II. fig. 12, 13). olal/es spinosus). Pentacta doliolum has simi- 2 Valentin, loc. cit. PI. Vll. fig. 135, 1. lar organs. According to Cuvier (Anat. Comp. 3 Valentin, loc. cit. fig. 143 ; a.nd Erdl, loc. cit. VII. 1840, p. 536) there is only a single brauchia fig. 13.' in the other remaining Holothui-inae. 4 The branchiae of Holothuria tubulosa have * [§ 90, note 3.) See, in this connection, Miller tin^s observations as to the structure of the extep- (Arch. 1850, p. 122), who has confirmed Ko. en- nal gills. — Ed. 92 TH..'] ECHINODERMATA. §-§ 91, 92. sive power, united with tlie action of the cloaca, enables them to receive into and expel from their interior the water of the sea/^^ The internal branchia3 of the Echiuridae consist of branchless tubes. In Hchiurus vulgaris, the two branchiie, which are very movable and open into a kind of cloaca, have, on their exterior, infundibuliform, ciliated pro- tuberances ; and to each of these there is internally a corresponding cili- ated sac, capable of being inverted. The very bright-red, vascular net- work which is spread over these branchiae, communicates with the great ventral vessel at the posterior extremity.'''' § 91- II. Among the organs which are not exclusively respiratory, are the ambulacra of the Echinodermata pedata, and the oral tentacles of the Ho- lothurioidea and Sipunculidae, — organs Avhich are used also for prehension and locomotion. These ambulacra and tentacles have always a cavity which communicate;? directly with the proper vascular, aquiferous system. Their whole interior is covered throughout with ciliated epithelium. This aquiferous system has, until recently, been taken by anatomists as a special vascular one, or confounded with it. Its water serves partly to distend the ambulacra and tentacles, as shown above (^ 77), and partly for respiration, which is performed by the vesicles over which ramify the branchial vessels. These vesicles are therefore like internal branchiae, their vessels being bathed by the water of the sacs, and that of the cavity of the body. Usually this system consists of a ring situated between the vascular rays of the mouth, which sends canals to the oral tentacles and to the sides of the body. These canals always pass along by the rows of anibulacral vesicles, with which they communicate by lateral branches. § 92. In the Echinodermata pedata, this aquiferous system has the following modifications : In the Crinoi'dea, and Ophiuridae,*^' only traces of it have been found. In the first, there is an apparently aquiferous canal for the tentacles, situated directly under their furrow. This may be regarded as forming a j)art of such a system. In Pentacrinus, it is simple, but in Comatida, it is divided at several points by simple septa.*-' In the Asteroidae, this system is highly developed, the central ring being provided with pediculated and often elongated vesicles.'^' The main 5 There is found, bat inconstantly, it would XXI. fig. 17) it wculd appear that Ophiurus has appear, upon the trunk of the branchiie of some an aquiferous system. )l')lothuriuae particular pedunculated coeca, which '^Müller, Abhandl. d. Berl. Akad. 1S41, p. 234. in Hohailschia rnarmorala have been regarded as 3 These ])yrlfi)rm vesicular appendages are al- urinary organs by Jaeger (Ue Holothuriis, &c., ways situated between the principal vessels of the I'ab. III. flg. 9, g.). But they require further rays, varying both as to number and volume, ami Livestlgation.* biding sometimes entirely wanting. Astropecten ö Forbes and Goodsir (Froriep''s neue Not. bispinosus has only five ; Asterisciis verrucii- No. 392, p. 277, fig. 12, e. — 19). latun, Astropecten pentncanthu.i, and Astera- l i'rom the figures of Delle Cliiaje (loc cit. Tav. canthion glacialis, have ten, in paii-s. In tliis •(§ 90, note 5.] For many new details upon 3/« «er. Arch. 1850, p. 129-155 (Si/napta, Chir- the respiratory system of the Ilolothurioldea, see odota, and Molpadia). — Kd. <$, 92. THE ECHINODERMATA. 93 trunks from this oral ring pass along the furrows of the rays close to their external surface. The ambulacral vesicles into which their lateral branches open, are sometimes simple/*' or, from a kind of sulcation, have a heart-like form.'^' In the Echinoidea, the oral ring wants the pyriforra appendages,'"' and its main trunks pass along the internal wall of the shell. The am'julacral vesicles of the oral membrane are conical ; but the others are flattened, overlap each other in a tile-like manner,"'^' and have a distinct branchial, vascular network.'*" The aqueous oral ring of the Holothurinae has hollow appendages (ten- tacular vesicles) projecting into the cavity of the body.'"' It has also, in many species, a larger, longer, and sometimes double, coecal vessel {Am- pulla Polia?ia).^^°' Opposite the tentacular vesicles, the ring sends off' to the oral tentacles, vessels which are often arborescent and comparable to external branchiae ;'^^' while, between these vesicles, arise five other vessels which descend along the internal surface of the body. As usual, they send off lateral branches to the generally very small ambulacral vesicles. ''-' In a few species only of the Synaptinae, the aquiferous ring has hollow appendages. '^^' From it pass off' vessels both to the tentacles and to the sides of the body. As the ambulacra are here absent, the five main trunks do not give off lateral branches.'"' In the Sipunculo'idea, the aquiferous system is least developed. As yet there has been found only a liquid moved by vibratile cilia in the doubly- laminated cavity of the lobulated tentacles of the Sipunculidae. With this cavity, two vesicles of Poll communicate, thus indicating the presence of an aquiferous system."^' last species they are only slightly developed ; in Astropecten. aurantiacus there are three to seven vesicles, opening by a common duct into each of the five angles of the aqueous vascular ring ; see Delle C/iiaje, loc. cit. II. p. 296 ; Tiedemann, loc. cit. p. 52, Taf. VIII. ; Konrad, loc. cit. fig. 3 ; and Meckel, Syst. d. vergleich. Anat. V. p. 32. Hei-e should be mentioned also the glandular corpuscles which are attached to the aqueous vascular ring, and which resemble in some respects the glandular organs of the vascular sanguineous rings of Echi- nus, pointed out by Valetitin ; see Delle Chiaje, loc. cit. II. Tav. XXI. fig. 12, 14 ; Tiedemann, loc. cit. Taf. VIII. o. o., or fVagner, Icon. zoot. Tab. XXXII. fig. 2, m. 4 Ophidiaster, Asteracant/iion. Luidia ; see Müller and Troschel, loc. cit. Taf. XI. fig. i. 5 Astropecten ; see Konrad, loc. cit. fig. 4. I am not yet settled upon the question whether the aquiferous system of the Asteroidae is filled by the extremity of the ambulacra, or by the oral ring. I have not been able to convince myself of the pres- ence of an opening at the extremity of these first. 6 Delle Chiaje (loc. cit. Tav. XXVI.) has given very detailed figures of the aquiferous system of Echinus and Spatangus ; but he has confounded it with the sanguinqpus vessels of the intestinal canal. ^ yalentin, Mouogr. &c. PI. CXXXIV.— CXXXVI. 8 The branchial vessels ramifying upon the flat- tened ambulacral vesicles appear to have been seen by Monro (V'ergleichung des Baues und der Phy- siol, der Fische, 1787, p. 91, Taf. XXXIII. fig. 13-15 ; or Cyclopaedia of Anat. and Phvsiol. 11. p. 35, fig. 14). Krohn {Muller's Arch. "lS41, p. 5) has accurately described them. It is affirmed that the ambulacra of Echinus can be filled with water through an opening of the suclcer at their extremity, and that it is discharged from the aquif- erous system through ten openings between the teeth ; see Tiedemann, loc. cit. p. 81 ; Falentin, Monogr. &c. p. 84, or Repertor. f. Anat. 1843, p. 237 ; and Monro, loc. cit. p. 92. a Tiedemann, loc. cit. Taf. II. fig. 4, e. e. fig. 6, m., and Delle Chiaje, loc. cit. Tav. YIII. IX. !<• Tiedemann, loc. cit. Taf. II. fig. 4, a. a. fig. 6, g. ; Delle Chiaje, loc. cit. Tav. IX. fig. 6, f. (Hoiothuria tubnlosa). 'I The position of the tentacular vesicle seems exactly adapted to enable them to force, during their contraction, their water into the tentacles, thus causing the prominence and development of these last. I am yet uncertain if they are not aided by the vesicles of Poli. ^^'ith some Holo- thurinae, as with Cladolabes spinosus (Atlas zool. du Voyage de I'Astrolabe. PI. VII. fig. 3, f.), and with Pentacta doliolum according to my own observations, the aquiferous ring has only one ve- sicular appendage, and it would be questionable whether this is analogous to a tentacular vesicle, or to one of PoU. Thyone and Cuvieria have, according to Ko- ren (loc. cit. p. 20, 36, fig. 2, 11), only a single ■large, vesiculiform appendage upon their aqueous ring. 12 See Delle Chiaje, loc. cit. Tav. IX. fig. 6 {Holothuria tiibnlosa) ; but here also the aiiuife- rous is confounded with the sanguineous system. '■i In Chirodota Doreijana, and fiisca, theso hollow tentacular vesicles are very apparent ; see Atlas zool. du ^■oyage, &c., loc. cit. PI. VII. fig. 16, PI. VIII. fig. 3. H quatrefages, loc. cit. p. 58, PI. IV. fig. 1, PI. V. fig. 5. 15 That the tentacular membrane of the Sipun- culidae has the function of a branchia, is indicated 94 THE ECHINODERMATA. f.*^ 93, 94. § 93. III. In nearly all the Echinoderms, as has been seen, all the viscera are bathed with water which certainly aifects their delicate blood-vessels. It is very probable that from ciliated epithelium covering the entire cavity of the body and the viscera this water circulates in a definite manner. It is rejected at last through many respiratory openings, through which also fresh water is introduced. In the Ophiuridae, there are in each inter-radial space two or four large openings of this kind, leading into the cavity of the body.*^' In the Asteroidae, water passes freely in and out the cavity of the body, through small contractile trachean tubes, which have been known for a long time, and which are very numerous upon the back. They are cov- ered within and without with ciliated epithelium, and have an opening at their extremity,'^' As yet it is unknown how the cavity of the body of the Echinoidea and Holothurioidea receives the water. Only in Synapta Dmiernaea, have there been found proper respiratory openings ; these are four or five papillae, covered with cilia, concealed at the base of the oral tentacles, and connecting with the cavity of the body through a narrow canal. '^^ In the Sipunculidae, the water is received through an opening at the posterior end of the body.^^'^ CHAPTER VIII ORGANS OF SECRETION. § 94. The Echinoderms appear to have special organs of secretion. In differ- ent parts of the body there are glandular organs, the real nature of which, however, has not yet been determined.'^' by the presence of delicate and tortuous vessels, observed by Grube (Muller^s Arch. 137, p. 253) upon that of Sipunculus nudus. The same con- clusion might be drawn from the liquid moved by cilia oV>served by myself in the interior of the ten- tacular lobules of Pliascolosoma granulattnn. Grube (Mutter's Arch. 1837, p. 251, Taf. XI. fig. 2, P.) has seen in Sipunculus nudus the two vesi cles of Poli, communicating with the cavity of the tentacular membrane. 1 Mutter and Troschel, loc. cit. Taf. IX. X. 2 E/irenber/f, Abhandl. d. Berl. Akad. 1835, Taf. Vtll. fig. 12, e. ; aM Stinrpey, Cyclopsedia of Anat. &c. I. p. 615, fig. 2«8, C. * [ End of § 93.] In Echinaraclinius and Cty- peaster Af^assiz has observed that trachean tubes, similar to those of the Asteroidae, perform the function of carrying the water in and out of the body. They are situated chiefly along the margin 3 Quatrefages, Ann. d. So. Nat. loc. cit p. 64, PI. V. fig. 7, f. 4 The manner in which the water enters into the interior of the Echluridae is not quite clear to me from the description of Forbes and Gondsir (^Fro- riep\s neue Not. No. 392, p. 277). I The attention has already been directed to these glandular organs, when speaking of the parts to which they are attached. The calcareous sac, or stony canal as now understood, of certain Aste- riae, can scarcely be regarded as organs of secre- tion. of the disc, emptying first into a circular tube, anal- ogous to the circular tube of the Discophora, from which extend ramifications i Ito the main cavity of the body ; see Compt. rend. 1847. — Ed. ^§ 95j 96. THE ECHINODERMATA. 95 CHAPTER IX. ORGANS OF GENERATION. § 95. Although most Echinoderms have extraordinary powers of reproduc- tion, yet this, apparently, is not for the multiplication of the individuals, for they do not reproduce either by fissuration or by buds. The Holothurioi'dea alone, perhaps, form the exception.*^' All propagate by the sexual organs of separate male and female individuals, and her- maphroditism is very rare. The eggs which are usually round, are covered by a thin chorion, and contain beside a little albumen, a variously colored vitellus with its germi- native vesicle and dot.® The sperm is always milky, and the spermatic particles which are unaffected by sea-water, are nearly always composed of a round or oval, rigid body, to which is attached a delicate, very active tail.<3) § 96. Externally, the organs of both sexes exactly resemble each other, and especially during the interval of procreation ; but at the sexual epoch they often differ in color. Their situation is very varied, and they are composed of simple or branched tubes, with proper excretory ducts. These last, however, are sometimes wanting, and then the contents of the former escape by rup- ture, and, falling into the cavity of the body, pass out through the respira- tory openings. Here, as in the Polyps and Acalephs, the copulatory organs being absent, the water is the medium of the fecundation of the eggs, by bringing the spermatic particles in contact with them. 1 The Uolothuria, which, when captured, dig- 3 See, for the spermatic particles of Astera- ■charge all their viscera through the mouth, can, cantftion, Sola-fter. and Echinus (KölUker, according to Dalyell {Froriep's neue Not. No. Beiträge, loc. cit. fig. 1-4, and P'alentin^ Monogr, 331, p. 1), not only reproduce all these, but also &c. fig. 168), of Holothuria and Synapta can divide spontaneously into two or more parts, (fVagner, Icon. zoot. Tab. XXXII. fig. 13, and each of which becomes a complete individual. This Quatrefag-es loc. cit. PI. V. fig. 2). Those of sim- multiplication by fissuration occurs also, perhaps, ilar form have been seen in Coinatula by Müller with Synapta Duvernea : see Quatrefages, loc. (Monatsi)ericht d. Berl. Akad. 1841, p. 189, or the cit. p. 26. Abhandl. of the same, loc. cit. p. 2-35). Accord- 2 See the eggs of Comatula Europaea (^Mill- ing to Valentin (Repertorium, 1841, p. 301), /er, Abhandl. d. Berl. .4kad. 1841, Taf. V. fig. 17), those of Spntanirus violncevs have an elongated of Asteracanthion violaceus (IVagner, Prodro- body, pointed in front, with a very delicate hair-like mua, &c., Tab. I. fig. 3, or Carus and O/Zo, Erläute- tail. Those of Ophioderma longicauda, and rungstafeln, Hft. V. Taf. I. fig. 1), of Echinus livi- Ophiothrix fragilis, according to my own obser- dus and sphne.ra {Valentin Monogr. &c. fig. 167, vation, have a round body, with an equally deli- 169), of Holothuria tabulosa (^fVagner, Icon, cate hair-like tail.* zoot. Tab. XXXII. fig. 12), and of Synapta Du- vernaea (J^uatreJ'ages, loc. cit. PI. V. fig. 1). * [ § 95, note 3.] The spermatic particles of the are wide, and of zoological import. Thus ft is Echinoderms are developed, like those of the other sometimes round (Asterias, Urastes), sometimes Radiates, in special cells, and like them also have, pyriform (Echinocidaris), and sometimes long- I think, invariably a cercaria-form. The differ- comcaX {Mellita). — Ed. «Qces in the shape of the head of these particles 96 THE ECHINODERMATA. <§, 97. § 97. In the Crinoidea, these organs, in the form of tubes, are situated urrder- the soft perisoma of the pinnulae, and probably are without proper excre- toi-y ducts. '^' In the Ophiuridae, they consist of lobular, pedunculated sacs, which are suspended in pairs in the inter-radial spaces of the disc. These ten organs are usually deeply fissured, and the lobules thus formed appear as so many proper sacs attached to the peduncle. <-> These last are sometimes subdivided also.® Sometimes each organ, divided in its whole length into lobules, is turned in the shape of a ram's horn.'** The peduncle of these organs is directed towards the mouth, but it is yet uncertain whether their contents escape this way or fall into the cavity of the body. In the first case, the pedun- cle would be the excretory duct ;'^* and in the second, the eggs and sperm would escape through the respiratory openings.'^' In the Asteroidae these organs consist of varicose lobular sacs, situated in the angles of the inter-radial spaces.'"' In those species which are without an anus, there are no proper genital openings ; '''' these openings are also wanting in those Asteroidae which have an anus.'^' In these last, the sperm and very small eggs pass into the cavity of the body, and probably have their escape through the respiratory openings.'^"' But in some species,'"' there are upon the back and near each angle of the inter-radial spaces two small approximated plates, perforated by small openings [Laminae cribrosae). These are the simple openings of these organs, which here consist of multi-ramose sacs, situated all along each side of the inter-radial septa, to the common duct which opens through one of the plates. The number of these genital sacs varies widely in the different genera of the Asteroidae. In many, a single trunk of them hangs on each side of the inter-radial septa ;''-* in others, there is a whole row of them;"''' and in others still, there are two rows attached to the dorsal surface of the cavity of the body, and extending into the rays.'^'" In the Echinoi'dea, these organs descend along the internal surface of 1 The development of the genital organs of 8 As in Astropecten and Luidia. Comatula was first observed by Dujardin, who 9 As in Ophidiaster. asserts that the red vesicles situated on both sides 10 According to Sars, the ventral surface of the- of the tentacular furrows secrete, during the epoch disc and arms of the female Echinaster xanguin- of rut, a very beautifully red liquid (L'Instit. No. o/entiis and Asteracanthiun Miilleri have at cer- 119, p. 268, or H'^ieg'mann^s Arch. 1836, II. p. tain times a kind of incubating cavity, in which the 207). Thompson has seen the eggs of Comatula eggs remain during their development. He thinks, escape in clusters through the openings of the pin- they get there from the cavity of the body, through nulae (Edinb. New Philos. Jour. No. XX. p. 295, particular openings upon the ventral surface of this or Froriep''s neue Not. No. 1057, 1836, p. 4, fig. last ; see Wiegmann's Arch. 1844, I. p. 169, Taf. 8) ; while, according to Müller, they escape by YI. fig. 1, 2. rupture (.\bhandl. d. Berl. Akad. 1841, p. 234, Taf. The genital parts of Echinaster snnguinolentu» V. tig. 17, 18). have been described with mm;h detail by SarSy 2 Ophioderma longirauda, and Ophiolepis Faun, littoi«. Norveg. p. 48. scolopendrica ; see Rathki, Forie.p^s neue Not. H Asteracanthion ruhev/t, a,r\(i Solaster pap~ No. 269, p. 65 ; and, Neueste Schrift, d. Natur- pnsim ; see Müller and Trosckely loc. cit. Taf. forsch GeselUch. in Danzig. 111. lift. IV. 1842, p. XII. fig. 2-4. 116, Taf. ri. fig. 3, 4. 1-' Kr.hinaster, Astrogonium, Asteriscus, and 3 Ophiocoma nigra; see Rathk^, Danzig. Ctenoaiscn.^. Schrift. &c. loc. cit. Taf. II. fig. 5-7. '"^ Astropecten, Oreaster, and Culcita ; sea 4 Ophinthrix frngilis. Tiedemann, loc. cit. p. 61, Taf. VIII. L. L. ß Rnthki, loc. cit. 1-1 Archaste.r, Chaetaster, Luidia and Ophidic ß Müller and Troschel, loc. cit. p. 133. aster ; see Müller and Trusc/iel, loo. cit. TaC 7 Müller and Troschel have very interesting XII. fig. 5. details upon the various arrangements of the geni- tal organs uf the Asteroidae (loc. cit. p. Hi}. <^97. THE ECHINODERMATA. 97 the shell, filling the empty spaces between the double rows of anibulacral vesicles. They consist of widely ramified, deeply interlocked coeca, having always proper excretory ducts, which open upon the genital plates of the back of the shell/''^ There are here always five of these organs, and the genital plates, alternating with the ocellary ones, surround the anus/^*'^ In some species of the Clypeastridae, and Spatangidae, there are, perhaps, only four of these organs, judging from that number of the plates. *''^^ In the Holo- thurinae, these organs have a very diflerent arrangement. They consiKst of widely-branched coeca,''*** floating, as loose clusters, freely in the cavity of the body, and opening through a single common excretory duct, situated below the osseous circle, and between the oral tentacles. The testicle, which is of a whitish color, consists of a cluster of cylindri- cal sacs, branched and interlocked with each other.''"* But the ovary is pale red, very long, branched, a littie flattened, and extends even to the posterior end of the body.'-"* As the only exception among these animals, the Synaptinae are her- maphrodites. But it should be stated that we know of them only througlx Synapta Duvernaea. It is said that here the testicles and ovaries are united in one and the same organ.'-" Three or four long cylindrical sacs float in the cavity of the body, and have an excretory duct which opens back of the osseous circle. At the eoocli of procreation, vesicular pro- longations appear on their interior sui-face, in which are formed spermatic particles. The spaces between these prolongations are filled by a pultace- ous mass, in which appear eggs.'--* In the Sipunculidae, and Echiuridae, there are only two or four simple cylindrical contractile pouches attached to the ventral wall. It is yet undetermined whether their contents escape by rupture, or through special openings. &) 15 The separate sexes of Echinus were first is something so remarkable, that one cannot but shown by Peters ; see Muller's Arch. ISiO, p. believe tliat Quatrefases has here taken the 143. parent sperm cells for the eggs. 16 See Tiedemann, loo. cit. p. 85, Taf. X. fig. 1, ü3 in Sipunculus, and Phascolosoma, there is 4, 8 ; and especially l^alentin, Monogr. he. p. 103, observed on each side, a little front of the anus, a PI. VIII. sac attached to the side of the body (see Delle 17 ViliÜi Echinantlius, Mellita, Rotula, Scutella Chiaje, loc. cit. Tav. I. fig. 5, s. s. and Grube,. (see A^assiz. Monogr. des Scutelles), and Spa- Muller's Archiv. 1837, Taf. XI. fig. 1. V). tangus arcuarius, and ovatiis, I can count only These have been regarded as genital organs. In four genital plates, while in Encope, and Clypeas- Sipunculus nudus, Grube has found eggs not ter, I find five •, yet Valentin (ßepertorium, 1810, only in these sacs, but in the cavity of the body p. 301) expressly speaks of five genital organs in also. It may, therefore, be questioned if the eggs Spatan^us violaceus. escape from the sacs into the cavity of the body, \i fVasner and Valentin were the fii-st who whence they are expelled through an opening at its noticed the sexual differences of Holnthuria tubu- posterior extremity, or if they are accidentally losa ; see Froriep's neue Not. No. 249, p. 99. introiluced from without with the water, during 10 See fVagner, Icon. zoot. Tab. XXXII. fig. 11 respiration. In this last case, these sacs should (Hnlothuria tubulosa). I have already remarked have excretory ducts; and there are, indeed, in (^ 86), that the white cylindrical pedicelte, taken Sipunculus nudus, two external fossa; oppusite by some zootomists as testicles (Delle Chiaje, loc. the point of insertion of the sacs (see De He cit. I. p. 9T, Tav. VIII. fig. 1. o.), are distinct from Chiaje, loc. cit. Tav. I. fig. 2, f.), and in which it the genital organs, and communicate dii'ectly with is said, there are two very small openings. Ac- the intestinal canal. cording to Forbes and Goodsir, tlie genital sacs 20 See the Catalogue of the Physiol. Series, &c., of the male Echiurus vulgaris cortain a seminal loc. cit. IV. PI. XLIX. fig. 1. c. {Holothuria tub- liquid, with very active spermatic jiarticles, while ulosa). those of the female are filled Witt .'ggs ; see Fre- 21 Quatrefages, Ann. d. Sc. Nat. loc. cit. p. 66, riep's neue Not. loc. cit. p. 28j fig. 20, 22, 12, PI. IV. fig. 1, q. PI. V. fig. 1. f. f.* 22 This deep confusion of the organs of two sexes * [§ 97, note 23.] For the sexual organs of Sipunculus, see Peters (Mailer's Arch. 1850, p» 9 98 THE ECHINODERMATA. ^98. § 98. The few obsei'vations hitherto made upon the embryology of the Echino- dorms belong solely to the Asteroidae. Here, the vitellus undergoes the uflual segmentation, and then is changed into a long, cylindrical, infusorial embryo, covered with cilia. A tew days after, four papillae are formed upon the anterior part of the body, and by these the embryo is attached to the walls of the incubat- inof cavity (Brutholile). It then begins to be flattened laterally, and upon one of these lateral surfaces, ray-like tentacles appear, while the margin of the body forms five angles, upon the extremity of each of which is a red pigment dot. Then the cilia upon its surface disappear, and the young individual, deprived of its papillae and set free, moves about by its ambulacra. ^^^ 1 These interesting observations of Sarx (JViez- mann's Arch. 1837, I. p. 404, IS-ii, I. p. 169, Taf. VI. fig. i-22) were made upon Ec/iinaster san- guinolentus, and Asteracaiithion MilUeri. He has also observed that during the development, the point of attachment is gradually changed, until it reaches the back ; thus supporting the view that the madreporal plate is the relic of this last, which, in Comatula, has been well compared by Müller and Troschel (Syst. d. Ästenden, p. 13-1), to a button, since from it the young individuals are attached by a pedicle, as Thomson has shown upon (formerly) Pentacrinus Europaeus ; see Zeitsch. f. die Organisch. Physik. 182S, p. 55, and the Edinb. new Philos. Jour. 1836, p. 296, or Fro- riep^s neue Not. No. 1057, 1836, p. 1. The asser- tion of Sars {fViegmann^s Arch. 1844. I. p. 176) that the animal which he formerly called Bipin- naria asterigera (Beskrivelser, &c., p. 37, Tab. XV. fig. 40) is probably only a developing As- teroid endowed with a great swimming ajipara- tus, deserves to be considered. The remark of DalyeU {Froriep''s neue Not. No. 331, p. 2) that the young of Holothuria are of the size of bar- ley-corns, and resemble white maggots, is not one that affords us any data upon the development of these animals. There remains, therefore, a vast field open to observers concerning the development of the Echinoderms. Sars (loc. cit. p. 47, Taf. VIII.) has furnished numerous data on the development of Echinaster. It appears, moreover, that all the Asteroidae are not developed after this type ; for, Koren and Danielssen (Ann. d. So. Nat. VII. 1847, p. 347, PI. VII. fig. 7-9) have shown that Bipinnaria ■asterigp.ra first observed by Sars, is a young As- teroid which moves by means of a i)Mrticular appendage, which is very complicated, and provided with numerous oars, — an appendage which is sub- sequently detacliea, but which continues then to execute natatory movements. There were, per- haps, sunilar appendages detached from young Asteroids that Mailer and ffagner found at Helgoland, and which they have described and fitfured under the name of Actinotrocha branch- lata; see Miiller^s Arch. 1846, p. 101, Taf. V. fig. 1, 2, and 1847, p. 202, Taf. IX. fig. 1-6. Various naturalists have noticed interesting facts on the development of the Echinidae in endeavor- ing to produce artificial fecundation. In the first of these experiments, by Baer, in 1845 (Bull. de. la Classe physico-math. de I'Acad. des Sc. de St. Petersburg, V. p. 234, Froriep^s neue Not. XXXIX. p. 36), the eggs of Echinus esculentus, and livi- dus, thus fecundated, were transformed, after a complete segmentation of the vitellus, into a round, infusoria-like body, covered with cilia. Diifossi and Derbes (Ann. d. Sc. Nat. VII. 1847, p. 44, and VIII. p. 80, PI. V.) followed still further, with Echinus esculentus, the development of these infusoria-like embryos. They gradually became pyriform, and acquired a peduncle at theii* smaller anal extremity ; while at the larger, oral end, ten- tacles and several long calcareous spines were developed. At the same time the digestive canal was formed in the interior of the body. A small marine animal, first described by Mül- ler (Arch. 1846, p. 108, Taf. VI. fig. 2, 3, and 1847, p. 160) under the name of Pliiteus paradoxus, has been recently found by this same naturalist to be the young of an Ophiura. This animal swims by means of vibratile cilia, and is supiiorted by a frame composed of ten diverging, calcareous pro» longations, resembling a painter's easel.* 382, Taf. IV. fig. A— II), and Krohn (Ibid. 1850, p. 368, Taf. XVI.). Peters has found that the fine whitish line de- scribed by Grabe as lying contiguous with the blood- vessel of the intestine is an oviduct, being filled with ova, which move along by the action of the cilia with which it is lined. Connecting with this ovi- duct are botryoidal appendages, situated on the intestine, and filled with eggs ; these are the ovaries. The eggs, when matured, escape into the general cavity of the body, and thence are transferred out- wardly through two brownish tubes, which open externally, and whose internal extremity is not closed, as has hitherto been supposed, but opens into the general cavity of the body. These tubes, or oviducts, have been regarded hitherto as respir- atory or secreting organs. Krohn'' s observations confirm those of Peters on this point. — Ed. * [ § 98, note 1.] The development of the Echino derms has been much and successfully studied of late, and chiefly by Müller, wlio, by several suc- cessive memoirs (see loc. cit.), has changed the zoological face of this class, beside making himself the great authority on all that relates to its embry- ology. The writings of Ai;assiz and others fur- nish also many details, but in any account I may give I shall depend mainly on the first-mentioned authority. ^98. THE ECIIINODERMATA. 99 The first condition of every Ecliinoderm is the 6ame, — an oval, ciliated body, resembling an in- fusorial animalcule, and without external organs, or distinction of parts. This is the starting-point, -and upon it succeed variations accomiing to the •different famiUes. Upon this ciUated body are developed, at one part, peduncles for its attachment to other bodies, while the rest of the germ increases in size, and assumes a star-fish form. The larvae thus formed may be divided into two groups : 1. Those of the Ophiuridae and Echinidae. 2. Those of the Asteroidae and Ilolothuridae. The first are somewhat hemispherical bodies, •with one edge of their truncated side prolonged into a single flat and wide process, which carries the mouth and oesophagus ; while from the oppo- site extremity project rods, of four, eight or more in number, and which form the internal skeleton. (See Ueb. d. Ophiurenlarven d. Adriat. Meeres. Taf. I. II.) These larvaj have a globular stomach in then- hemispherical portion, and from which pro- ceeds a short intestine terminating in a circular ■anus. They have, moreover, a ciliated fringe, •which consists of a ridge covered with large cilia, passing above the mouth and before the arms, com- pletely encircling the body in an oblique manner. With the second group there is no internal cal- careous skeleton, and they form 3IüUer''s Auricu- iaria (of the Ilolothuridae), and Bipinnaria (of the Asteroidae). The first of these are concavo-convex bean- shaped bodies, with an Irregular transverse fissure answering to the hilum of the bean, in which the mouth is placed. The margins of this fissure are •ciliated ; the anus opens on the ventral surface. The Bipinnaria closely resemble these last, but they have a distinct ciliated circle in front of the mouth ; as they increase in size, the anterior part of their body is covered with long processes, which "vary according to different forms. Out of these larvae, all of which have a strictly "bilateral symmetry, the more or less radiate adult Echinoderms are developed by a process which is a sort of internal gemmation. The changes and variations of this metamor- phosis I will give in Müller''s own words : " 1. The change of the bilateral larva into the Eohinoderm takes place when . the larva yet re- mains an embryo, and is universally covered with •cilia, without a ciliated fringe. A part of the body •of the larva takes on the form of the Echinoderm ; the rest is absorbed by the latter (a part of the Asteroidae, Eckinaster, Asteracanthion^ Sars). " 2. The change of the bilateral larva into the Echinoderm takes place when the larva is perfectly organized ; that is, possesses digestive organs and a special ciliated fringe. " The Echinoderm is constructed within the Plu- teus like a picture upon its canvas or a piece of embroidery m its frame, and then takes up into itself the digestive organs of the larva. Hereupon, the rest of the larva vanishes (Ophiura, Echinus), or is thrown off {Bipinnaria). " 3. The larva changes twice. The first time it passes out of the bilateral type with lateral ciliated fringe into the radial type, and receives, instead of the previous ciliated fringe, new locomotive larval organs, the ciliated rings. Out of this pupa-condi- tion, the Echinoderm is developed, without any part being cast off (Jlolothuria, some Asteroidae). "If we call embryonic type the condition ia which the animal leaves the egg, and when the internal organs are not yet developed, we have four stages or types, — the embryonic type, the larval type, the pupa type, and the Echinoderm type. The animal may pass from either of the first three forms into the Echinoderm, or may run through them all." See Ueber. d. Larven u. d. MetamoriJh. d. Holoth. u. Aster, p. 33. See, also, a review of Muller^s researches, by Huxley (.\im. Nat. Hist. VIII. 1851, p. 1), and by Dareste (Ann. d. Sc Nat. XVII. 1852, p. 349). These results are highly interesting in both a zoological and a physiological point of view, and I need only suggest their important relations to the doctrine of " alternation of generations." In this connection, it may be proper to allude to another point. It is well known that Vogt (Na- turgesch. d. lebend, u. untergegang. Thiere. I. Liefer. 3, p. 25-1) has removed the Bero'id Medusae from the Acalephae to the " Molluscoida," re- garding them bilateral animals. In a private letter from Agassiz, there is a passage bearing du-ectly on this point. He says : " The young Echinoderms are structurally and morphologically homologous with Bero'id Medusae, showing that Beroüds are genuine Radiates, and truly belong to the class of Acalephae, and cannot be referred to the MoUuscoids. These relations will be plain by comparing Taf. I. fig. 6, of Muller's Larven und d. Metamorph, d. Ophiuren und Seeigel. 1848, with the figures of PI. VIII. of Agassiz'' Memoir on the Berold Medusae, in the Mem. of the Amer. Acad, of Arts and Sc. Vol. IV." For further writings on the development of the Echinoderms, see Müderes papers, published in his Arch. 1848, p. 113 ; 1849, p. 84, 364 ; 1851, p. 1, 272, 353 ; but these papers are all included in his large memoirs already given. See, also, Krohn, Beitrag, zur Entwickelungsgeschichte der Seeigle- larven, 1849, and in Muller's Arch. 18.51, p. 338, 344, 368 ; and Desor, Muller's Arch. 1849, p. 79. — Ed. BOOK FIFTH. HELMINTHE S CLASSIFICATION. § 99. It is very difficult to characterize the class Helrainthes, for it con- tains animals having widely dissimilar organization. On this account, the separation of its groups, and their distribution among the other classes of the invertebrata, has been attempted. But such various difficulties have arisen from this, that for the present, it is best that all these animals should remain together. If a common character is not furnished by their structure, it must be sought for in their manner of life ; for nearly all are parasites, ^^> and during their whole life, or at least during some of its periods, seek their abode and nourishment in or upon other living animals, ORDER I. CYSTIC I. The body is swollen in the form of a bladder, and filled with a serous liquid. Digestive and genital organs are wanting.'-' Genera : Echinococcus, Coemirus, Cysticercus, Anthocephalus. ORDER IL CESTODES. The parenchymatous bod3'^ is riband-like, having often incomplete trans- verse fissurations ; often it is wholly divided transversely into rings. Di- gestive organs are wanting. The genital organs of both sexes are com- bined in the same individual, and generally are often repeated. Copulatory organs are present. Genera : Gymnorhynchus, Tetrarhynchus, Bothriocephalus, Taenia, Tri- aeaophorus, Ligu/a, CarynphyUacus. 1 J«ffi/!7/tt,'a is the only exception to Ulis. some Cestodes ; from wliich it mi^lit be inferred 2 The head of the sexless Cystici, as to its form, that they are only the larval forma of these last. Its hook and suckers, strikingly resembles that of ^99. THE HELMINTHES. 101 ORDER in. TREMATODES. The body is parenchymatous, and usually flattened. The intestinal canal, which is often branching, has a mouth, but nearly always is without an anus. The genital organs of both sexes are combined in the same indi- vidual. Copulatory organs are present. 'Genera : Gyrodactylus, Axme, Octohothr'mm, Diplozoon, Polystomum, A^pkhcotyhis, Aspidogaster, Tristoimmi, Monostovmm, Ho/ostomum, Gasterostomum, PentastomumJ^ ORDER IV. ACANTHOCEPHALL The sack -like body is flattened, transversely striated, and swollen cylin- ■drically by the absorption of water. Digestive organs are wanting. The genital organs are situated in separate individuals. Copulatory organs are present. Genus : EcJiinorhynchus. ORDER V. GORDIACEI. The body is filiform and cylindrical. The digestive organs are without an anus. The genital organs are situated upon separate individuals. Copulatory organs are sometimes present. Genera : Gordius, Mermis. ORDER VI. NEMATODES. The body is sack-like and cylindrical. The digestive canal has a mouth and an anus, and passes in a straight line through the cavity of the body. The genital organs are situated upon separate individuals. Copu- latory organs are present. * In this connection, and especially in reference to the remarks made by the author under §. 99, it may be well to notice that Fan Benedeti does not regard the Linguatulae as true Helminthes, but that they belong rather to the division of articulated animals, — coming nearest to the Lerneae. His reasons are the following : " These animals, on theh* extrication from the egg, are provided with two pairs of articulated feet terminated by hooks. " The nervous system differs from that of the Lerneae only in having two cords which forna the ganglionic chain, separated throughout their whole length, whilst in the Lerneae they are separated for only half their length. " In both cases the males are comparatively very small. The ovisacs of the females are equally bulky ; but In the Lerneae which live in water they project externally, whilst in the Linguatulae, which always live in a dififerent medium, they remain in the interior. 9* " Besides the ring of nerves, the sub-CESophageal ganglion, and the cords which represent the ganglionic chain, the Linguatulae are provided with different ganglia representing the great sym- pathetic. I detected four perfectly distinct ganglia spread over the sides of the lower surface of the oesophagus in the new species from the Mandrill. In another species M. Blanchard detected these ganglia and stomato-gastric nerves; but he referred them to the system of the nerves of relation or those of animal life, judging, at least, from the name which he has assigned to them. " Another point, which, however, had not escaped the attention of naturalists, is that the muscles exhibit in their primitive fibres the transverse lines which are not met with in the lower ani- mals." See Bull, de '.'Acad. Royale de Belgique, 1S4S, XV. No. 3. See also Blancka^d, Comp. liend. 1850, XXXI. p. 629. — Ed. 102 THE IIELMINTIIES. § 99. Genera : Sjjhaerularia, Trichosoma, Trichocephalus, Filaria, Aiigjiillula, Pkysaloptera, LiorkyncJu/s, Lecanocephahis, Cheiracanthus, Gnathosovia, Ancyr acanthus, Spiroptera, Hedruris, Stro?igylus, Cucullaims, OxyuriSy Ascaris. BIBLIOGRAPHY. Goeze. Versuch einer Naturgeschichte der Eingeweidewürmer. Blank- enburg, 1782. Zeder. Erster Nachtrag zum vorhergehenden "Werke. Leipzig, 1800. Brera. Vorlesungen über die vornehmsten Eingeweidewürmer des menschlichen lebenden Körpers. From the Italian by Weber. Leipzig, 1803. Rudolphi. Entozoorum Historia Naturalis. Amstelaedami, 1808— 10, and Entozoorum Synopsis. Berolini, 1819. Bremser, lieber lebende Würmer im lebenden Menschen. Wien, 1819. Translated into the French under the title : " Traits zoologique et physio- logique sur les Vers intestinaux de VHomine, par Bremser, traduit par Grundler, revu et augmente de notes par De Blainville. Paris, 1824." To this Leblond has added a new Atlas. Paris, 1837. Brejyiser. Icones Helmiuthum. Viennae, 1824. Cloquet. Anatomie des vers intestinaux Ascaride lombricoi'de et Echin- orhynque geant. Paris, 1824. CrepUn. Observationes de Entozois. Gryphiswaldiae, 1825 ; and Novae Observationes de Entozois. Berolini, 1829. Mehlis' excellent remarks upon this work in the Isis, 1831, p. 68, 166. Bojanus. Enthelminthica, in the Isis, 1821, p. 162. Nitzsch. In Ersch's and Gruber^s Encyclopaedie, articles : Acantho- cephala, Acephalocystis, Amphistoma, Anthocephalus, Ascaris, &c. Creplin. In the same work, articles: Distomum, Echinococcus, Echino- rhynchus, Eingeweidewürmer, Enthelminthologie, &c. Delle Chiaje. Compendio di elmintografia umana. Napoli, 1833. Leuckart. Versuch einer naturgemässen Entheilung der Helminthen Heidelberg, 1827 ; and his Zoologische Bruchstücke, Hft. I. Helmstädt 1820, and Hft. III. Freiburg, 1842. Baer. Beitrage zur Kentniss der niederen Thiere, in the Nov. Act, Acad. Leop. Carol. Vol. XIIL p. 525. Nordmann. Micrographische Beiträge zur Naturgeschichte der wirbel losen Thiere. Berlin, 1832. E. Schmalz. XXIX. Tabulae Anatomiam Eatozoorum illustrantes Dresdae, 1831. These contain mostly copies. C. Th. E. Siehold. Hehninthologische Beiträge und Jahresberichte über die Helminthen, in Wiegma?in's Arch, für Naturgeschichte. Dlesi?ig. His excellent Monographs in the Annalcn des Wiener Muse ums. F. J. C. Mayer. Beiträge zur Anatomie der Entozoen. Bonn, 1841 li. Owen. His excellent article, Entozoa, in the Cyclopaedia of Anat- omy and Physiology. Dujardin. Histoire naturelle des Ilelminthes. Paris, 1845. *$. 100. THE HELMINTHES. 103 ADDITIONAL BIBLIOGRAPHY. The following are among the more important contributions to the Anat- omy of the Helminthes which have been published since the issue of the original work. I should mention, however, that I have not had very much access to recent German contributions in this department, from the tardi- ness with which such matters reach this country. However, I am happy in not being ignorant of the late publications of Siebold, who is truly at the head of Helminthology. Blanchard. Recherches sur I'organisation des Vers., in the Ann. d. Sc. Nat. VII. 1847, p. 87, VIII. 1847, p. 119, 271, X. 1848, p. 321, XI. 1849, p. 106, XII. 1849, p. 1. Van Beneden. Recherches sur I'organisation et le developpement des Linguatules (Pentastoma, Rud.), &c. in the Mem. de I'Acad. de Bruxelles, 1848 ; also, in Ann. d. Sc. Nat. 1849, XI. p. 313. Note sur le developpement des Tetrarhynques, in the Bull, de I'Acad. de Belgique, XVI. 1849. Recherches sur les Vers Cestodes, in the Mem. de I'Acad. de Belgique, 1850, XXV. Siebold. Ueber den Generationswechsel der Cestoden nebst einer Revi- sion der Gattung Tetrarhynchus, in Siebold and Kdliker's Zeitsch. II. 1850, p. 198. üeber die Verwandlung des Cysticercus pisiformis in Taenia serrata Ibid. IV. p. 400. Ueber die Verwandlung der Echinococcus-Brut in Taenien. Ibid. IV. 1853, p. 409. See, also, various valuable though small contributions, in the form of letters to Siebold, in Siebold and Kölliker'' s Zeitsch. IV. p. 52, 116, 451, 454 ; as well as the references in my notes. — Ed. CHAPTER I. CUTANEOUS SYSTEM. § 100. The body of the Helminthes is generally surrounded by a firm skin, which may be separated into a thin epidermis, and a pretty hard dermis. The epidermis of the adults is never ciliated ; but not unfrequently it has horny spines pointing backwards, which sometimes are limited to the ante- rior part of the body, and sometimes spread over a large surface, in trans- versely serrated rows.^^' In the first case, the spines serve to attach them I In many Nematodes, Acanthocephali, and Tre- sum, scnbrum, ferox, and perlatum (Ibid. Tab. matodes, the epidermis is spinous like a rasp. X. and Nordmann, Mlcograph. Beiträge. Hft. I. These spines are simple '\a Liorhynchus dentic- 1a.(. J^.), And Peiitastomum denticulatum (Die- ulatus, Lecanocephalus spinulosus (according sins;, loc. cit. I. Abth. 1, Taf. III. fig. 10-13). to I)iesin^, Annalen des Wiener Museums, II. But they are polydentlculated in Cheiracanthus Abth. 2, 1839, Taf. XIV. fig. 14-20), Echinorhyn- (Diesing; loc. cit. II. Hft. 2, Taf. XIV. XVI. chus pyriformis, and hystrix (Bremser, Icon. XVII.). Helmut. Tab. VII.), Distomum lima, maculo- 104 THE HELMINTHE3. ^101. to other animals, and therefore will be specially described with the locomo- tive organs. With most of the Nematodes, the epidermis has very fine and closely approximated transverse folds, which are but occasionally so prominent that the body appears annulated.'-' Sometimes, but rarely, the body is also plicated in a longitudinal manner.''^' The dermis has a fibrous structure, consisting of two fibrous layers, — one longitudinal and the other transverse, — which cross each other at right angles ; and of two other layers, which intersect each other more acutely.'*' The skin of these animals has a great absorptive power which during life is voluntary, but which contin- ues to a certain extent after death, so that then these worms often swell enormously, and sometimes burst. '"^^ §101. Directly beneath the skin of the Cystici, and Cestodes, are found hard •corpuscles containing carbonate of lime, and which may be regarded as the vestige of a cutaneous skeleton. But, as they are scattered here and there more deeply in the parenchyma, they certainly may be compared to the spicula and calcareous net-works found in the skin of many Polyps and Echinoderms. Oval or discoid, they are usually of equal size in the same individual. Sometimes, however, they present irregular and unequal forms. Always colorless and transparent, and composed of concentric layers, they refract the light like small vitreous bodies. In Taenia, Triaenophorus, Bothriocephalus, and the young of Echino- coccus, they are subcutaneous, and more or less scattered ; but in the wrinkled and vesicular body of Coenurus, and Cysticercus, they are so very abundant that they form quite thick layers. They are absent in the cau- dal vesicle of Cysticercus, but in Coenurus, and Echinococcus, they are found in the vesicular walls beneath the delicate epithelium which lines the interior of the body.''' 2 Tliis is so, for instance, with the anterior •extremity of Liorliynchiis denticulatus, and ■Strong-ylus annulatus, mihi (from the trachea _ of the wolf). The epidermis of Ascarix ni^rovenosa has such long and loose folds that its body, seen laterally, has a fringed appearance. 3 Excepting the longitudinal folds of the epider- mis, which form lateral wings of variable form and length at the cephalic extremity of the Nematodes, or on both sides of the extremity of the tail of many males of this order (Bremser, Icon. Helminth. Tab. IV. fig. 20-2i), I have as yet found the epi- -dermis longitudinally plicated over the whole ■body only with Strongijlus striatus, and inflexus. 4 These difl'orent dermic layers are distinct, espe- <;ially with Qordius and Mermis ; see Diijar- ■dhi's figure in the Ann. d. Sc. Nat. XVIII. 1842, PI. VI. I have found this structure also in A.ica- ris my.slax, microcephaLa, liistomuTn echina- tum, hians, linea, and in Monostomum verru- coKum. In Amphistomum /^i^anleitm, Diesing (Annal. Jahrg. 1816, p. 225, Taf. V.) has described and figure Haer, in Nov. Act. Acad. &c. XIII. pt. 1, p. short; and in Dis/u/iiuiii (i/i/iiiidir.ulatmn, it is 536, Taf. X.XVIII. ; also D/e.sjnfi-, Med. Jahrbuch, entirely wanting, and ciiis'iiu.wiily the intestinal d. k. k. österreichischen Staates. XVI. 1834, p. 423, bifurcation is directly behiml llii' pharynx. fig. 8-11. Ü In Monostomwn, Amphistoinum, Ilolosto- ü Bucephalus pal ymorphus is prohahly alaxvaS <§>108. THE HELMINTHES. 11^ this canal is simple, straight, and ends posteriorly in an anus."^ In many Trematodes, the intestinal tubes have in all their course simple or ramified caeca, and in some, these caeca are so fully developed that the intestinal canal appears to fill the whole body/*^* The intestinal walls here are very thin, but this does not prevent peristaltic and anti-peristaltic movements, by which their contents move backwards and forwards, and are often rejected through the mouth.*'' o § 108. In the Nematodes, and Gordiacei, the intestinal canal passes straight fron* the mouth which is at the anterior extremity, through the cavity of the body to the anus, which, in the fii-st, opens front of the caudal extremity.*" In very many Nematodes, the mouth has nodosities and swellings, but it is seldom that its cavity has horny, tooth-lilce processes.'-' From the mouth extends a long and very muscular oesophagus, which is usually dilated claviform at its lower extremity. When the oesophagus is very long, it has one or more constrictions.'^' It is nearly always composed of three longitudinal muscles which are united by longitudinal seams. The triangular cavity circumscribed by these muscles is lined by a very firm epithelium, which is sometimes horny, and in some species so thickly set in the clavate dilatation that it resembles a masticatory apparatus.**' The intestine consists of a straight tube, with thin walls and without dilata- Qasterostomum ; and the species above men- tioned I have discovered in the intestinal canal of Perca ßuviatilis, and Lucioperca. 7 See Miram, Owen, and Viexing, loc. cit. The opening at the posterior extremity of many Trema- todes, and by many Ilelminthologists taken for an anus, belongs to a special secretory organ, which will be mentioned hereafter. 8 In many species alhed to Monostomum trigo nocephalum, the two intestinal tubes have simple caeca upon both sides of their entire length. In Octobothrium la7iceolatu7n, the structure is the same ; see Mayer, Beitr. p. 21, Taf. III. fig. 3. These lateral caeca are more or less ramified in Oc- tobothrium palmii/iini. s/n.nlliitiun, Merlangi, Polyxtormim apjirnilirii/ntti m. .mil Tristomum. eloiigatuni {LeucAiirt, Zinl. l'.ruclistücke, Hft. 3, p. 26, 51, Taf. I. fig. 4, c. 1). Taf. II. fig. 5, d. ; Nordmann, Microgr. Beitr. Hft. 1, p. 79, 81, Taf. Vir. fig. 2, Taf. v. fig. 6 ; and Baer, Nov. Act. Acad. Leop. XIII. pt. 1, p. 665, Taf. X.V.XII. fig. 2). 'With Distomum hepaticum, these vnmiRca.- tioa? are very fully developed ; see Mehlis, Observ. de Distomate, fig. 1, 2, 7, 8. In the very remark- able genus Diplozoon, the digestive canal consists of a single tube which traverses the whole body upon the median line, and sends ofl' laterally ramified caeca, while at the point of junction of the two bodies of the animal it dilates into a stom- achal cavity ; see Nordmann, loc. cit. lift. 1, p. 67, Taf. V. fig. 2. The blackish ramifications of Polyntomum integerrimum, and which have been regarded by Baer (Nov. Act. Acad. Leop. loc. cit. p. 682, Taf. X.Y.YII. fig. 7, 8) and other authors as a digestive canal, belong to the subcu- taneous pigmentary net-work already mentioned. 3 The digestive canal of Trema.odes is usually partly fiUed with blood which they have absorbed, and partly with brown or yellowish chyme ; it is therefore evident how, from the thinness of its walls, it would, when empty, entu-ely escape the observation. 1 Among the Nematodes, and Gordiacei, there iu# are, moreover, species which have very rudiment- ary digestive organs. In Sphaerularia bombiy tliere is nfeither mouth nor anus, and in the place of the intestinal canal there is a row of long sacs- clinging together, and around which the genital or- gans are coiled (IViegmann^s Arch. 1838, I. p. 305). In Filaria rigida, living in the intestine» of Aphodius Jimetarius, I have found no digest- ive canal whatever (Miil/er^s Arch. 1836, p. 33). In the various species of Mermis, there is a dis- tinct mouth, oesojjhagus and intestine, but this last ends in a caecum. I have been unable as yet to positively determine a mouth with Gordius aqua- tic us ; the anus is certainly wanting, and it might- be questioned if the two tubes which traverse th& body should be regarded as an intestine ; se& fViegmann^s Arch. 1843, II. p. 305. - AVith StrongyLus armatus, hyposto?nus, den- tatus, and tetracanthus, the entrance of the mouth is provided with a circle of horny teeth, which ar» moved by special muscles ; see Mehlift, Isis. 1831, p. 78, Taf. II. fig. 5, 6. With Spiroptera stron- gylina, I have seen the enth'e internal surface of the mouth provided with a spiral, horny swelling. In Cucullanus, there is a very comi)licated appa- ratus for opening and closing the mouth, composed of solid, horny pieces. 3 With Anguillula fluviatilis, Oxyuris vermi- cularis, Ascaris acuminata, brevicaudala, dac- tyluris, oxyura, and vesicularis, the oesophagus has tills enlargement.- But it is divided into two portions by a ijrominent constriction with Cucul- lanus elegans, Physaloptera alata, Spiroptera anthuris, europtera, obvelata, and crassicau- da. In Trichocephalus, it is very long, and has behind very many constrictions, which are succes- sive at short intervals ; see Mrnje.r, Beitr. &c. Taf. I. II. With Trichosoma falconum, it is equally long and divided into many sections, which give it an articulated aspect. i By many Helminthologists this tube has beea called Oesophagus, and its dilatation slomachus. 114 THE HELMINTHE3. §109. tions, and which terminates in a short muscular rectum. The proper intes- tine is of a brown, greenish, or dirty yellow color, which is due to its walls being formed of compact cells filled with colored granules. The loose and cellular walls, having very feeble peristaltic movements, are surrounded externally by a kind of dense peritoneum, and lined internally by a very fine epithelium.'^' In some species of Ascai-is, the intestine is lengthened into a caecum at its junction with the oesophagus.''"' § 109. There are observed, here and there, only traces of appendant organs of the digestive canal. In many Trematodes, there are upon each side of the neck, two more or less developed cords or canals, of a cellular aspect, and of a pale yellow color by direct light. They pass towards the mouth, open perhaps into its cavity, and have a function, probably, like that of salivary organsß^ In many Nematodes, two or four caeca extend from the cephalic extremity along the (.esophagus, and as they open distinctly into the oral cavity, it is, therefore, the more probable that they should be regarded as salivary organs.'-' The same signification should be given to the coecal appendage found in many species of Ascaris, which extends from the constriction of" the oesophagus to the beginning of the intestine.'''' Hepatic organs have been found nowhere but in the Nematodes; but it may be that the granular cells in the thick walls of the intestinal canal, take their place. 5 This epithelium has sometimes special inequali- ties, which, with Ascaris osculata, and spicu/ige- ra, form a regular zig-zag series, resemljling the valves of the intestinal mucous membrane of some vertebrates. With Ascaris aiicta, they have the form of long, sharp villosities. 6 This caecal appendage, accompanied usually ■with a constriction of the posterior end of the oesophagus, was first observed by Mehlis (Isis. 1831, p. 91, Taf. II. fig. 16, 17, IS). It is found with many Ascaris, but its length is very variable. In Ascaris hetertirn, srmiteres, and ensicaudata, scarcely beyond the ; w\dle in Ascaris depres- .1 iiiiirrnnrifa, it ri-;iclicÄ to ,:vj\\<, aiul ill A^ruri.s- s/,i. I llic 110. THE HELMINTIIE3. 11^ CHAPTER VI CIRCULATORY SYSTEM. § 110. Most of these animals have a vascular system. The circulating liquid is usually wholly colorless, and often contains vesicular or granular cor- puscles, which are difficult to perceive from their delicacy and transparency. The circulation is due to the general contractions of the body or of the walls of the vessels. In the Acanthocephali, the vessels have no proper walls, but are spread out, as has already been said ( ^ 106), in the subcutaneous parenchyma. There are two larger, lateral canals, which pass from the neck to the caudal extremity, sending off laterally numerous small canals, which anastomose with each other. A similar net-work is found in the proboscis through its whole length/'^ These two canals connect also with the Ze/Hm'sci, upon each side of the neck. These last, of which there are always two upon the sides of the proboscis, passing from the neck to the cavity of the body, are usually riband-like, and composed of a finely-granulated parenchyma, which, like the cutaneous one, has a system of vascular canals/-* In most species of Echiriorhynchus, this system consists of a main canal upon the border of the lemniscus, from which are sent off inwardly, nu- merous small branches. These last form the net-work which fills the paren- chyma of the proboscis.'^' In many,^* the lemnisci are surrounded by muscular fibres, which, con- verging to the posterior extremity of these oi-gans, form two short muscles, which, in their turn, are blended with those passing obliquely to the pro- boscideal sheath. The point of junction is at a short distance from the place where they are detached from the subcutaneous muscular layer. Each lemniscus is constricted into a narrow neck at its base, which passes into the skin at the base of the proboscis. The junction of the cutaneous with the lemniscian vascular system occurs at this point, as is indicated by the contained liquid passing backwards and forwards between the two from 1 This vascular system, taken by many Hel- norhynchns claviceps, they are longer than the mintholoi^ists for a digestive canal, has been flg- body, and lie coiled in its cayity. In Echino- ured by freÄfr«»i7> (De Helminth Acauthocephalis rhynchus gibl/osus, hystrix. and strumosus. Tab. II. fig. 10,111. flg. 10, 12, 21), and ßuro I« they arc disoi ml and very sli.rt. <(Echinorhynchi strmnosi Anat. 1836, flg. 1, S). 'i Echinoiiiynclms an^usiatus, haeruca, poly^ The movements of the nutritive liquid may be morp/ius, proteus, and gilibosus. As a wide distinctly seen by placing these animals alive and exception, the ijrincipal canal occupies the median undilated as natural under the microscope. One line of the lemuiscii, and sends off laterally small will then be quickly convinced that the circulation branches, with Echinorhynchiis gigas. Here is due to the general movements of the body. If and there its course is broken by oval, vohmiinou*, Echinorhynchus is placed in much water, the transparent and apparently vesicular bodies ; see absorption distends not only the body, but the Westrumb loc. cit. Tab. 11. flg. 7. Similar bodies -canals of the vascular system are so fllled that the in the lemnisci and subcutaneovis parenchyma, are subcutaneous parenchyma is swollen, and the found with Echinorhynclins claviceps ; see Miil- skin is raised here and tliere into vesicles. ler, Zool. Danica. Tab. LXI. tig. 3. These bodies 2 With Eckinorhynckus angustatus, aciis, are, moreover, regular neither as to their number Jusiformis, proteus, and polymorphus, the two nor pu! In the Trematodes, this system consists of a contractile net-work spread over the whole body ; and in which are two larger trunks, which pass along the sides of the neck and body.^-^ 5 3Iehlis (Isis, 1S31, p. 82) affirma to have seen on the neck of Echinorhynchua gi^as two small orifices by which the lemnisci open outwarils. But I have l)een unable to see them in this species, or others of this same genus. If they really exist, they will shed light upon the doubtful functions of these organs. From what we know of their struc- ture, it is not improbable that they belong to the nutritive system, and transude a liquid which bathes and nourishes the organs in the cavity of the body.* 6 With the Nematodes, the liquid appears to transude through the walls of the intestine into the cavity of the body, and there bathe, without a vas- cular system, all the organs. The riband-Uke organ found in the Filaria piscium (see Wiegmann's Arch. 1838, I. p. 310), and which I have also found in Ascaris osciilata, has the same vascular rami- fications as the lemnisci of Echinorhynr.hus gi- gas, and the vesicle-like bodies are not wanting upon the course of the principal canal. Perhaps they also transuile the nutritive liquid, for I have not found any communication between them and the intestinal canal. The two lateral enlargements also, which, as already mentioned (§ 102), are extended between the longitudinal muscles of the skin, have often been regarded as sanguineous vessels ; but I have observed with them neither longitudinal nor lateral canals. t 1 These lateral vessels, regarded by some Hel- minthologists as intestiiml tiili^?, nivc off in their course no lateral braucli' -, r\<' pt iIm--' transverse canals. With the articulated ( '..^t «Irs, ili'-'se last are always situated at the i)osteriMr extremity of the articulations, thus giving a ladder-like aspect to the entire vascular system. They are also found, however, in Caryophyllaeus rnutabilis, which is not articulated. * [ § 110, note 5.] The observations of Jfext- rumb and liurow on the circulatory system of the Acanthocephali, have recently been thoroughly verified by Ulanchard, who has illustrated it with excellent figures ; see Ann. d. Sc. Nat. 1849, XII. p. 21, and Rögne animal, nouv. Eilit. Zoophytes, I'l. XXXV. fig. 2. — Ed. Plainer (Mailer's Arch. 1838, p. 5'72, Taf. XIII. fig. 4, 5) aftirms to have seen semilunar valves- at the orifices of the transverse canals of Taenia solium. The four lateral cervical vessels which I have observed not only in Taenia, but also in Bothrio- cejihalus, and Cysticercus, may be traced with perfect distinctness in Taenia cynthiformis, and serrata, to the vascular ring which siuriaiuds the proboscideal sheath. With Caryophylliuiix rnu- tabilis, and Taenia ocellata, wliich are without a proboscis, this vascular ring does not exist any more than with Bothriocephalus ; here also the four lateral vessels widely ramify in the head, and form by iiiiiistoinoses, a distinct net-work. Both- rioctphatiix rliniceps has a similar organization. It should, moreover, be here observed that from the contraction of its very thin walls the vascular system will easily elude the observer. Ü The vessels of the Trematodes are remarkable for their prominent flexures ; see Vistnmum cir- rigerum, tereticolle, duplicatum, and the various species of Diplostomurn {Nordmann Wicrogr. Beitr. lift. 1, Taf. II. fig. 8, IV. fig. 5, 6). One should not confound with the sanguineous vessels, as has often been done, the very finely-ramified canals of the excretory organ, which will hereafter be mentioned. Thus I think that the vascular net-work of Distomum hepaticum described by Bojanus (Isis, 1820, p. 305, Taf. IV.) belongs to this excretory organ. Laurer also (de Amphis- tomo conico. p. 10, fig. 22), has not carefully dis- tinguished them ; and Nordmann a])pears to have fallen into the same error (loc. cit.). With Diplostomum,thti vessels open each side into a large reservoir situated at the extremity of the body. ■ Between these two receptacles, th«i excretory organ jiasses to tlie extremity of tho body, and Nordinaiin has taken its orifice a3 t [ 5 110, note 6.] Berthold (Uebcr den Bau des Wasserkalbcs. &c. loc. cit.) has described a vascular system with the Gordiacei; but Blanchard (Ann. d. Sc. Nat. 1849, XII. p. 7) has failed to- confirm his statements after very careful research. — Ed. ^112, THE HELMINTHES. 117 CHAPTER VII RESPIRATORY SYSTEM. § 112. A respiratory system has not yet been found with certainty in the Helminthes. The pedunculated vesicles of many Nematodes, situated under the skin, and projecting into the cavity of the body, and which have great absorp- tive power, have been compared to trachean pouches and branchiae ; but their structure is so little known, that any opinion as to their function ought to be deferred/^' A remarkable fact is the presence in some Trematodes of extremely active vibratile lobules, situated intermittingly on the inner surface of the walls of the vessels. <-> It may be questioned if these vessels have a special function, different from that of the others. They somewhat resemble the aquiferous system of the Polyps, Acalephs, and Echinoderms, and like it, belong, perhaps, to the respiratory system. They differ, however, in not having openings which communicate outwardly ; but, probably, they receive by endosmosis, water absorbed by the skin.*^> But another objection to this view, is, that in this order there has been found nothing like blood-vessels. belonging to the nutritive vessels. Tlie nutritive liquid of the vascular system differs from the coarsely-granulated excretion of the excretory organ, by its homogeneous and colorless aspect. It is remarkable that in Distomum tereticolle this liquid has a reddish color, which, in the finest capillaries has a yellowish cast ; see fFiegmann^s Arch. 1835, I. p. 59. H. Meckel, likewise, thinks that the above-de- scribed vascular system of the Trematodes, is in du'ect communication with the secreting organ peculiar to these Ilelmintlies ; see MuUer''s Arch. 1846, p. 2, Taf. I. fig. 2.* 1 Bojanux (Isis, 1821, p. 187, Taf. III. fig. 51- 65) aflirms to have observed in Ascaris lumbri- coides these pedunculated vesicles, which are found also in Ascaris depressa, and Strongylus saigas, in comiection with the lateral swellings ; but this throws no light upon the nature of these vesicles, for we are yet ignorant of that of these swellings. Tlie stigmata wliicli he affirms (loc. cit. p. 187, Taf. III. fig. 56) to have observed upon these lines with Ascaris acus, are, according to my own observations, only sulxiutaneous ceU-like bodies. 2 I have quite distinctly seen these vessels with Diplozoon paradoxum, Aspidosaster concki- co/a, Distomu-m echinatum, and an allied species of this last from the intestine of Falco apivorus. * [§ 111, note 2.] Van Beneden /'Ann. d. Sc. Nat. 1852, XVIII. p. 23) has recently expressed doubts upon the presence of a circulatory system I am yet uncertain if the vibratile organs found in the neck of Distomum globiporum and nodu- losum (IVie.gmann's Arch. 1836, I. p. 218), and in the parenchyma of Distomum duplicatum be- hind the ventral sucker, are of the same nature. Ehrenberg (JViegmanri's Arch. 1835, II. p. 128) was the first who observed this ciliary move- ment in the vessels of Diplozoon. When the motions of these lobules are free, there is a rapid current of the liquid, as Nordmann has remarked (Microgr. Beitr. lift. I. p. 69). But if an animal is compressed between two plates of glass, and their motions thus impeded, it will be quickly seen tliat these last are the cause of the circulation ; in fact, when the lobules cease moving, the colorless, homogeneous, and, without doubt circulatory liquid, is no longer perceived. 3 Burmeister (Handbuch d. Naturgesch. 1837, p. 528) compares, not without reason, this system to the trachean system of insects, the first being aqueous, and the second aerial respiratory organs, thus confounding this vascular system of Helmin- thes with the excretory organ and duct found in most Trematodes. There may be, however, a com- parison between these two systems, if we except the insects with stigmata, and take those which are aquatic and have a comi)letely closed trachean apparatus (see below), admitting no air from with- out. with the Cestodes and Trematodes, but see the beautirul piates of Blanchard, Ann. d. Sc. Nat. 1848, X. PI. XI. — Ed. 118 THE IIELMIXTHES. ^113 CHAPTER Yin, ORGANS OF SECRKI'ION. § 113. No orga is of secretion have been found, except in the Trematodes and Nematodes. In most of the Trematodes, there is, upon the median line of the posteriDr part of the body, a contractile sac, which usually opens out- wards, '^^ at the caudal extremity, and seldom at the posterior part of the back.*-' This sac is single, <■''' bifurcate,*^' or multiramose. In the last case, its branches are spread usually over the whole body/'' Its walls are quite thin, and therefore, it is seen with difficulty when wholly contracted or empty. It contains a colorless liquid filled with numerous granules or vesicles, which, during the contractions, pass up and down, or escape through the external opening.*''' This organ is sometimes so crowded with clear, solid corpuscles, composed apparently of earthy matter, that exam- ined by reflected light, it has a cretaceous aspect.*'^' In many Nematodes, there is on the ventral surface and at a variable distance from the head, a small oblique opening surrounded by a sphincter. In some species, two canals pass from it and run backwards on each side of the intestinal canal ; and in others, there are also two other canals which extend forwards in the same way. The use of the colorless and homoge- neous secretion of these organs is yet unknown.***' 1 This opening, known as the Foramen caudate with Distomu7n, Holontomuni, Monostomum, Aspidoganter, and Diplostomum, has formerly been cumparefl to an anus by Nardo (Heusin- ger^s Zeitsch. für organische Phys. 1827, I. p. 68), and by Baer (Ibid. II. p. 197). Mehtin (Observ. de Distomate,p. 16) having shown that it belonged, in DistomuTK hepaticum, to a particular organ ■which is ramified like a vessel, has properly re- jected this analogy ; see Isis, 1831, p. 179. With the larvae of Trematodes, known as Cercaria, Bucephalus, and Distomum duplicatum, the base of the tail is thrust into the excretory opening of this organ, and its contents cannot escape until the animal has lost the tail. 2 Amphistomum. 3 Monnxtomum faba, Dixtomum cirrisferiim, Gasteroxtominn Jimbriatum, and Bucephalus jiolymorphus. 4 Distomum chilostom.um, claviserum, lima, maculosum, tereticolle, varieiratum, and many species of Monostmnum, — where the two closed ends of the sac often extend to the cephalic ex- tremity. With Distomum appendiculatum , the two branches of the excretory organ utiite directly behind the oral sucker. With Aspidoi^aster coii- chicola, it divides into two canals near the Fora- men caudate, which extend to the anterior ex- tremity. Ill Amphistomum, two similar canals wind from the head along each side of the body, w the middle of the posterior back, where they open outwards, after having formed by reunion a pyri- form reservoir. Laurer (De Amphistomo conico. ji. 10, fig. 22) has given a figure of this reservoir, in which he ha^! confounded the secretory canals with the nutritive vessjls. 5 Beside Distomum, hepaticum, Holostomum. urni^erum, the Distoma also with a spinous head, have a widely-ramified excretory organ ; see Mehlig, Isis,1831, p. 182. 6 With the spinous-headed Distommn militare, and echinatum, this organ is often so reduced in substance, that here and there are perceived only isolated groups of the ramified canals. 7 The solidity of tliese corpuscles may have been the reason why Ehrenberg (Symb. Physic. Anim. Evertebr. Ser. I. Phytozoa entozoa) has taken those of Cercaria ephemera for eggs, and the two canals of the excretory organ for ovaries ; and why Nordmann (Microgr. Beitr. lift. 1, p. 54, Taf. I. fig. 7) has regarded their escape from the body with Distovium annuligerum, as an act of ovi- position. The corpuscles of this kind found in the excretory organ of certain Trematodes, as for instance in a larva of Monostomum known as Cercaria ephem- era, remind one from their astiect, of the small cilcarcous subcutaneous bodies of many 'V'ae/ua«, and it may be asked if they are not an effete mate- rial, which, not being contained in projier organs, is with these Helminthes thus subcutaueously deposited. « This organ, to which I first called the attention in the dissertation of Bagge (I)e evolutione S;r. 13), is comi>osed of two canals whicti run back- wards in Strongylus auricularis, Ascaris brevi- caudata, and acuminata {Basse, loc. cit. fig. 30, A. B.) ; and in Ascaris dm-ti/tiiris, -auiI pauri- para, mihi (from the iiiir^tiiin.i ■fisludii smeca), of two anterior and p i-^hiiMi- (finals, the cununoii opening of which is near llie middle of the body. <§>>§» Hi, 115. THE HELMINTHES. 119 CHAPTER IX. ORGANS OF GENERATION. § 114. Although most of the Helminthes propagate by means of genital organs, jet there are a few species which multiply hy fissurat ion and gemmation. T\\Q.fissuration\iiüXwAja transverse, and differs from that of the' Proto- zoa and Zoophytes in the fact that complete individuals are not produced, . there being only a separation of certain organs from the perfect animal, as, for instance that of the segments of the body in the Cestodes. This fissu- ration is complete or incomplete. In the first case, occurring in the Taenia, the segments are detached from the body, and continue to live independ- ently, without, however, ever forming a new individual. ^^' (j-emmation has been observed in the sexless Coenicrus and Echinococcus. In Coenurus cerebralis, it is incomplete. The buds are formed on the internal surface of the parent-vesicle, and never separate from it, nor become perfect individuals. They have only a head and neck which pro- ject outwardly after the complete development. In Echinococcus, however, the gemmation is complete. The buds appear as in Coenurus, but the young animals are sooner or later detachid and fall into the liquid of the parent vesicle. When completely developed, this vesicle bursts, and they are set at liberty. That their development occurs in this way is shown by their hanging by a cord, which, like the tail of Cercaria, is inserted into a fossa at the posterior extremity of the body. Like this last, also, this cord subsequently disappears, and the young animal moves freely about, by the aid of its double circle of hooks and its four suckers.'-' § 115. In those species which reproduce by male and female genital organs, these last are sometimes upon a single animal, and sometimes upon two separate individuals. The eggs and spermatic particles are formed after very differ- ent types. In all, the copulatory organs are extraordinarily developed. The Cestodes and Trematodes are hermaphrodites.*^' The structure of 1 The imperfect fissuration with Ligula and 2 See Chemnitz, De Hydatibus Echinococci ^riaenophorus is Mxmtad aXmost to a constriction hominis commentatio, 1834 ; Müller, u\ his Arch. of the lateral borders. With Bothriocephalus I806, p. CVII. ; and Siebold, in Burdach's Phys- punctatus, it is only here and there that a ring is iol. II. 18.37, p. 183. detached, and over most of the body the transverse 1 According to Nordmann (Microgr. Beitr. Hft. and opposite sulcations do not extend near to the 2, p. 1-11), Diesing (Ann. d. Wiener Mus. I. median line. With Sothriocephalus tetrapterus, Abth. 1, p. 9), and Miram (Nov. Act. Acad, the fissuration is more complete ; but even here, XVII. pt. 2, p. 636), the male and female genital there are only some incompletely limited rings organs of the genus Pentastomum, classed by among numerous others which are completely so. many modern Helminthologists among the Trema- Of all Helminthes the Taeniae have the most todes, are situated upon different individuals. But complete fissuration ; here not only is the separa- Owen affirms to have observed the opposite tion of the rings' indicated by a complete furrow, (Trans, of the Zool. Soc. of London, 1835, I. p but the rings are sometimes detached and live thus 325). The only way to settle this point is by independently. The separated rings of Taenia, analyzing accurately the contents of these organs ; solium, cucumerina, and others, move freely, and a method pursued by Valentin (Repertori\un III are fo individualized, that they resemble some 1837, p. 135), who found filamentoid spermatic Tremitodes. particles iu the organs of an apparently female 120 THE HELMINTIIES. «^115. the genital organs of the first is jet imperfectly known ; while that of those of the second is well understood. The female apparatus of the Treniato- des consists of a germ-forming organ (ovary), with its excretory duct; then, two others for forming the vitellus, which have also excretory ducts ; and then a simple uterus with its vagina. The male apparatus con- sists of testicles with their excretory canals, an internal seminal vesicle, a cirrhus-sac, an external seminal vesicle, and a penis.'-* The ovary consists of a round or pyriform '■^> reservoir, situated, usually, upon the median line of the body,'^* from which it is distinguished by its pale color and transparency. It is filled with simple round cells — the egg-germs. The nucleus of these cells is the germinative vesicle, and the nucleolus, the germinative dot.'"** The short and small excretory duct of the ovary opens at the commeiice- ment of the uterus. The organs which secrete the vitellus are two in num- ber, of variable length, and situated upon each side of the body near the dorsal surface ; they occupy either the cervical, the central, or the posterior portion of the animal, and sometimes extend over them all. They are nearly always composed of ramified caeca filled with white, granular, vitelline corpuscles. By reflected light these caeca appear through the skin as a white, ramified, botryoidal mass,"^' and from each of them, pass ofi" inwardly, numerous excretory ducts, which reunite opposite the ovary into two common canals. These last approach each other transversely, .and form a single canal upon the median line, which, after a short course, opens at the bottom of the uterus by an orifice which is common to it and the ovary. ''^^ J'entastomum taeniotdes, organs which are re- garded by Diesim; as caeca for secretuig the en- velope of the eggs. Since all the parts of the genital organs of Pen- iaatomuTn have not been examined with this same precision, I can give no opinion as to their use.* 2 See Siel/old, in fViegmann's Arch. 1836, I. p. 217, Taf. YI., and in MuUer's Arch. 1836, p. 232, Taf. X. fig. 1. 3 The ovary here is always smaller than the testicle, and sometimes as to form very closely resembles it, as in Distomuvi globiporum, and longicoUe, mihi (from the urinary bladder of Cottu.1 gobio) ; consequently it may easily be taken for a third testicle. 4 With Monnstomum, it lies wholly at the pos- terior extremity. 5 In Poli/stomum, Octobotkrium and Diplo- zoon, the germs are so large that they may easily be taken for perfect eggs. There is here, moreover, between the cell-wall and the nucleus (the germinative vesicle), quite a thick layer of albuminous substance, somewhat representing a vitellus. But in the other Trema- todes it is so thin as scarcely to be perceived. •> With the following Trematodes there is a wide deviation from this usual arrangement. In Dis- tomum lonsicoUe the organs producing the vitellus are two simple round caeca located behind the ventral sucker ; in Distomum cygnoides, they are two very small deeply-fissured bodies ; and in Distomvm gibbosum, there is one only, which is star-shaped and located at the middle of the body. <■ These organs, until now regarded as ovaries, secrete only vitelline cells. With most Treniatodes their nuclei are clear, and liave been taken for eggs. In eggs recently formed, one can always distinguish these cells from the germs. In passing the excretory canals they are compressed and elongated, but never run into each other. When these canals are crowded, they have the aspect of white cords, which have often been taken for- nerves. But when they are empty, they, as well as the vitellus-secreting organs, are almost invis- ible.t * [ § 115, note 1.] See upon this subject Fan Jieneden (Ann. d. So. Nat. XI. 1849, p. 326), who has described in detail the sexual organs of Lin- guatula Diesingii, and has shown the sexes to be separate. See also my note under § 99. — Ed. t [§ 115, note 7.] To say that certain organs secrete vitelline cells, is a little obscure, and no doubt Sicbold intended to convey the meaning that they secreted the plastic material out of which these cells are formed. I make this perhaps seemingly unnecessary reference to the matter, since it concerns the subject of the develojiment of the ovum. In the Ascaris, where the origin and development of the ovum can be satisfactorily studied, you first notice the germs as nucleolated cells, of which the nucleus is the future germina- tive vesicle and the nucleolus the germinative dot. These cells increase in size, and as they move along there appear in the liquid which lies between the nucleus and the cell-wall minute granules which ultimately become cells ; in this way the vitellus is formed, the formation being encogenous and not exogenous. These special organs or tubes therefore are vitellus-forming organs, in vir- tue of their secreting tlie formative material out of which the vitellus is formed within the original, nucleolated germ-cell. — Ed. 4115. THE HELMIXTHES. 121 The neck of the Internal seminal vesicle [Veslcida seminalis i7iterior), There is one common genital open- ing for the penis and vagina which are usually side by side, and out of which the penis often considerably projects. ''"' In most Trematodes, these tw^o organs are located at the anterior extremity of the body, and only in Holostomum, and Gasterostomum, are they removed to the other extrem- ity. ^^s> 8 The length of the uterus varies very much in different genera and species, and its coils are always irregular. With Monostomwn mutabile, and verriicosum, the oviduct arising in the poste- , rior extremity, passes in front with numerous transverse coiJs. y I have found one testicle only, in Amphisto- snum subclavatum, and Aspidof^asler conchicola, altliough I have seen three or four in Distomum appendiculatum, and cy^noides. 10 With Distomum ovatum, the two testicles are side l)y side behind the ventral suclier ; with Dis- tomum chiloxtomum., they are on each side of this sucker, and witli Distomum craxxum, mihi (from the intestine of Hirundo domestica)^ they are in .front of it, on each side of the neck. 11 With Distomum Innsicolle, lanceolatum, oxyurum, echinatum, globiporum., and Amphis- tomum conicum, the testicles have many depres- sions ; see Bojanus, Isis, 1821, Taf. II. fig. 25-27 ; Burmeister and Sielio/d, in IViesmann's Arch. 1835, II. Taf. II. 1836, I. Taf. VI. ; also Laurer, I)e Ampliistorao conico. fig. 21, 24, 25. With Amphislomum subtrii/uelrum, sinanteum, and Distomum /lians, the number and depth of these dei)ressions gives the testicle the aspect of a bundle of caeca ; see Bojanus, loc.cit. Taf II. fig. 14-17, and Diesing Ann. d. Wiener >Ius. I. Abth. 2, Taf. XXII. 12 In the testicles of the Trematodes, the devel- Of)ment of the spermatic particles occui's after the usual m(xie. The bundles which they form are separated in their passing the vasa deferentia, and they collect into irregular masses in the seminal vesicles. Their extremely active movements cannot be perceived unless they are quite isolated. When put in water they become twisted together, and assume a loop-like arraugemeut, — their motions instantly ceasing. For the development of the spermatic particles of the Trematodes, see KoUiker, Die Bildung du Saamenfäden in Bläschen, loc. cit. p. 44, fig. 31.* 13 These two vasa deferentia are sometimes blended together before reaching their destina- tion ; this is so in Disto?num variegatum, and longicolle. 14 The internal seminal vesicle is so extraordi- narily large in Distomum variegatum that it exceeds that of the ovary and two testicles. 15 This cirrhus-sac, together with the penis, is very long with Distomum /ima, macu/osum, variegatum, and ovatum ; but it is especially so with Aspidogaster conchicola, and Monostomum verrucosum. 1Ö The protruding cirrhus or penis of Distomum. holostominn is provided with small bunches ; and that of Monostomum verrucosum with num- berless little warts. 17 When the penis is protruded, it may then be seen how the contents of the vagina are emptied at its base. When the common genital opening is closed, the very flexible penis can be turned into the vagina and there discharge its contents, and in this way the self-impregnation of these animals may occur. 18 The common genital opening is usually sit- uated on the middle of the neck, and wiih Dis- tomum, it is directly in front of the ventral sucier. With Distomum clavigervm, and ovatum, it is upon the sides of the neck, and with Distomum, caudate, and holostomum, exceiJtianably, it is oa *[§ 115, note 12] TAner (7»/«//«?-'.? Arch. 1850, ured the spermatic particles of Po/j/.^/omuw ap- p. 602, Taf XXI. fig. 19) has described and fig- /je«(/(ct(/«i»m as Cercaria-form. — Ed. 11 122 THE IIELMIXTilES. §115. In the terminal, constrictel portion of the uterus, eggs, vitelline cells, and spermatic particles are often found mixed together. It is probably here that the eggs are formed, their fecundation occurring without copulation, and by means of the Vesicula seminalis interior. The succeeding folds of the uterus contain already, nicely-defined, oval eggs containing a germ and many vitelline cells. Their recently-formed envelope is still colorless, and so thin and flexible, that the peristaltic contractions of the uterus give it a variety of forms. But in passing from the uterus they lose this flexibility ; their envelope becomes more solid, — of a yellow and then a brown color ; and the whole, at the same time, undergoes a decrease in size, due prob- ably to a condensation of their substance. The eggs of most of the Trema- todes have an opercular opening at one extremity. ^^^' In the Gestodes, the walls of the genital organs are so very thin, and so intimately blended with the parenchyma of the body, that their structure and relations have not yet been well made out. With the exception of in Caryophyllaeus,^-^^ these organs are repeated many times one after another, having in the same individual difi"erent degrees of development. They are always most complete in the posterior portion of the body, being only rudimentary near the neck, while in the neck itself they do not exist at all. In the articulated Gestodes, each ring contains both male and female sexual organs ; and in their two Groups, the arrange- ment of these is the same as in the Trematodes. It is probable that the ovaries and the secreting organs of the vitellus are separate.*"^' In Ligula, Triaenophorus, and Bothriocephalus, the uterus consists, exactly as in the Trematodes, of a very tortuous tube filled with oval eggs.'-^^ But in the posterior extremity of tlie body. Its position is iudicated, even wlien the penis is not protruded, by a small papilla. With Octobotkrium, and Poli/siomum, there is a round muscular sac concealed directly behind this opening, which contains a circle of delicate horny ril)s, the lower extremities of which are bifid and form a support like a bownet. Mayer (Beitr. loc. cit. p. 21, Taf. lit. &g. 3, 6) has seen ten similar ribs with Octobothrium lanceolatum. I have found eijrht with Poly.itoinum intes^erri- iniim, and forty with Polystoinum ocellatum. Tlieir use is wholly unknown to me. I'J The eggs of the Trematodes have apparently only a single envelope. Among the normal eggs in the uterus may often be found others which are mal- formed, also very irregular bodies of a yellowish or brown color, formell almost enth-ely of the sub- stance of these envelopes. These bodies were most probably secreted by the walls of the uterus (the Tuba Fallopii) at a time when the ovaries and the secreting organs of the vitellus were inactive, SI that the substatice of the envelopes' was hard- ened bef)re receiving their usual contents. With Amphistomiim siihclavatum, Octobothrium lan- ceolatum, Polystoinum inte/i^crrimum, and ocel- I'ltum, and JJijilnznon paradoxum, the eggs are Vi;ry largt;, and in the last-named species their ex- tremities an! narrowed and lengthened into a spiral filament, wherefore one of these eggs has been taken for a testicle and penis ; see Nordmann Microgr. Ueitr. lift. 1, p. 7:5, Taf. V. VI. fig. 1, h.; also f^ogt, in Müller' s Arch. 18-11, p. 34, Taf. II. fig. 11. The eggs of Monoslomum verrucosnm, and gome other species of this genus which live in the iutestiue of Chelonia esculenta, have a very dif- ferent form ; they are oval and colorless, and at each extremity have two papillae, which are grad- ually developed into very long, sharp appendages ; see Dujardin, Hist. Nat. d. Hehninth. PI. YIII. fig. G, B. 3.* -" With Caryophyllaeus mutabilis, there is only a single cirrhus-sao upon the ventral surface of the posterior body, and from which a deUcate long penis often protrudes. 21 I think I have seen an ovary in each of the segments of Bothriocepha/us punctatus, and Tae- nia ooellata. As such, ought, perhaps, to be re- garded those organs which E.ichricht (Nov. Act. Acad. Leop. XIX. Suppl. 2, Tab. I. fig. 2, e, e) has considered with Bothriocephalus latus to be ovaries. The organs secreting the vitellus are a mass of irregularly arranged granulations situated upon both the dorsal and the ventral surfaces, and which have very fine excretory ducts. This mass, called by Encliricht (loc. cit. p. 25, Tab. I. fig. 5) the ventral and dorsal granules, cannot, together with its excretory ducts, be made out, excei)t when filled with the vitelline sul)stance. With Taenia ocellnta, the vitelline organs are limited to the sides of each segment, at the anterior border of which two main excretory ducts are easily seen j these form a single short canal in the middle of the body. In this same place are two transversely- jilaced oval sacs, and which are probably the two ovaries. 22 The uterine convolutions are generally in the middle of the body, and when filled with matm'e eggs, appear through the skin as a brown rosette ; see Eschricht loc. cit. Tab. I. II. {Uotliriocej-ha- lus latus). * [§ 115, note 19.] See also for the structure of p. 602, Taf. XX. ft|j the genital organä Tliaer, Müller's Arch. 18ÖÜ, culalum). — üb. 17 {Polystomum appenJi- <^llö. THE HELMINTHES. Taenia, it is a reservoir, composed of numerous ramified coeca, and inti- mately blended with the parenchyma of the body.*-''' The vagina is a nar- row, muscular canal, which usually opens close to the penis by a special orifice (Vulva), or by a common genital opening [Porus genitalis). It is difficult to decide whether the testicles, which always form the middle layer of the body, consist of a collection of inter-opeuing caeca, or of a single spirally-rolled tube. The cirrhus-sac with the Vas deferens open- ing at its bottom, is always very distinct. As in the Trematodes, it has a Vesicida se/ni>ialis, vfith. a. Ductus ejaculatorius and a muscular penis!'-'' The contents of the different canals, the seminal vesicle and the ejacula- toi'y duct, are always very active, filiform spermatic particles.*-''' The genital openings are upon the middle of the ventral surface, or on the lateral borders of the body ; but in those species where the sexual openings are separate, they are lateral for the male, and ventral for the female.*'-^' The eggs of the Cestodes, situated like those of the Trematodes in a spiral, pouch-like uterus, have also a similar structure. Their simple, oval, brownish-yellow envelope, has also, sometimes, an operculum. The eggs of Taenia have a very different structure ; the envelope is colorless, and of a very variable, and sometimes quite remarkable form.*'^' 23 With most Taeniae the borders of the cellular uterus are very difficult to distinguish. But its lateral caeca with Taenia oceLlata, and its arbo- rescent divisions with Taenia solium, are very easily seen ; see Delle Chiaje, Compendio di ELmintografia umana, Tav. III. fig. 10. 24 The cinhtis-sac is either short and pyriform, or very long. With very many Taeniae, as with Taenia amphitrica, lanceolata, muUistriata, scolecina, and seti^era, the penis has numerous small spines pointing backwards ; see Dujardin, Hist. d. Helm. PI. IX .-XI. That of Taenia infundibuliformis is surrounded with very large bristles ; and according to D ujardin (loc. cit. PI. IX. B. 210) this is also true with Taenia sinuosa. 25 By very slight pressure, the spermatic parti- cles contained hi the Vesicula seminalis of the ■ cirrhus-sac are pressed out through the penis ; this is so with Bothriocephalu.i punctatus, latus, Taenia cucumerina, planiceps (from the intes- tine of Hirundo urbica), inflata , pectinata, ser- pentulus, and villo.ius. As with the Trematodes, the spermatic particles here cease to move when put in water, and are twisted into loops.* 26 With Ligula, Bothriocephalus nodosus, latus, claviceps, ditremus, punctatus, and te- trapterus, the two geniUil openings are situated on each side of the ventral surface, while the penis protrudes from a special opening directly in front of the vulva ; see Mehlis in Isis, 1831, Taf. I. fig. 1, 2, aad Eschricht, loc. cit. Tab. I. fig. 5. With Bot/iriocephalus punctatus, there are two pairs of these openings upon each segment, one under the other, but in Bothriocephalus te- trapterus, these are side by side. With Triaeno- phorus, nodulosus,aiKl Taenia ocellata, the vulva is upon the ventral surface, and the penis upon the lateral border. With Bothriocephalus fra- gilis, proboscideus, rugosus, and with most Tae- niae, the cirrhus-sac and the vagina open by a common genital orifice upon the lateral border, and usually through a papilla. With Taenia cucumerina, and bifaria, mihi (from the intestine of Anas leucophthalmus), I have found an orifice of this kind upon the two lateral borders of each segment, and behuid which were the genital or- gans.! ^ Although I have m '■ seen either the germ {na- tive vesicle or dot in the eggs of the Cestodes, probably from their delicacy, yet I do not for a moment doubt their presence there, since Kölliker (Müller's Arch. 1843, p. 92, Taf. VII. fig. 44) has seen them in the eggs of a Bothriocephalus. Many species of this genus produce oval eggs which have a simple brown envelope. Of an oval form, Iiut col(-irless, are those of Caryophyllaeus, Ligula, Triaenophorus, Taenia literata, and scolecina. Those of Taenia amphitricha, bifa- ria, macrorhyncha,serpentulus, axxAserrata, are round, and have two colorless envelopes ; this is true also of the oval eggs of Taenia angulata, villosa, (fC. There are tln-ee of these envelopes with the round or oval eggs oi Bothriocephalus infundibul- iformis, proboscideus, Taenia porosa, lanceo- lata, ocellata, setigera, and solium. With Tae- nia infundibuliformis, and planiceps, each ex- tremity of the envelope is lengthened into a long and delicate appendage. Two smiilar but fibrll- lated appendages exist upon those of Taenia variabilis. With Taenia cyathiformis, the ex- ternal pyriform envelope of the eggs has, at its attenuated extremity, two round, bladder-like ap- pendages. Dujardin (Hist. d. Helm. PI. IX.- XII.) and I (Burdach's Physiol. 18-37, n. p. 201) have seen many other forms with the eggs of Taenia. The round and doubly-enveloped eggs * [5 115, note 25.] I have observed the de- velopment of the spermatic particles with Taenia. They are developed in special cells, and before they have escaped, are therein coiled up resembUng those of the coleopterous insects. They are simply filiform. — Ed. t [ § 115, note 26.] The Cestodes have been the objects of much careful study during the last few years, by Blanchard (Ann. d. Sc. Nat. X. 1848, p. 321) and Fan Beneden (Mem. Acad. Belgique, 1850, XXV.) and the sexual parts pretty clearly made out. They both agree tliat, internally, the male and female organs are wholly distinct, and therefore that impregnation of the ova must be by self-copulation. — Ed. 124 THE HELMINTHE3. *§. 116. § 116. In the Acanthocephali, the genital organs occupy a large portion of the cavity of the body. They arise in the posterior portion, and are supported by a lAgamentum suspetisorhun, which extends from this last to the base of the proboscideal sheath. In the females, there are neither proper ovaries, nor an uterus ; but in their place there are numerous oval, or round, flattened bodies of consider- able size, which float freely in the liquid of the cavity of the body ; they have nicely-defined borders, and are composed of a vesicular, granular substance, and, as eggs are formed within them, they may be regarded as so many loose ovaries.*" When the eggs have reached a certain size, they fall from the ovaries into the cavity of the body. At this time they are ovo-elongate, have only a single envelope, and contain both a vesicular and a finely-granular substance, but no trace of a germinative vesicle. They continue to in- crease in size, and two new envelopes are formed about them.^-* The umscular canal which passes ofi" from the simple vulva which is situated at the posterior part of the body, may be regarded as a uterus. At the point where it is attached to the Ligamentum Suspensorium, it becomes a campanulate or infundibuliform organ, whose borders float freely in the cavity of the body, and thus the whole is comparable to a Tuba Fal- lopii. The bottom of this bell-shaped organ comnmnicates with the superior extremity of the uterus by a narrow, valvular opening, which presents a lateral, semilunar fissure. This whole organ is endowed with very active peristaltic motions, by which the loose contents of the cavity of the body are absorbed ; and while the larger ovaries are thrown out, the little immature eggs are returned into the cavity of the body by the lateral fissure, — the more mature ones only, reaching the uterus.'''^ This uterus, which is of variable length, opens outwardly through a very short and narrow vagina. The males of Echinorhynchus have usually two oval or elongated testi- cles, one before the otlier, and attached to the Ligamentum Suspensorium. of Taenia cncumerina (Crep/tn, Observ. de 2 The long eggs of many Erhinorhynchi are EiiUizuis flg. 12, lo) and cra^erZ/or'/Ti/s, have the formed by the same process. Tliey are all colorless, remarkable arrangement of being gr.juped in tens and may be distinguished by the peculiar aspect to twenties, and each group is surrounded by a of their middle envelope which at both extremities gelatinous envelope.* is constricted like a neck. But those of Echino- 1 The ovaries of Echinorynchus were formerly rhynchun giitas form an excei>tion ; for they are taken both for mature eggs, and for cotyledons; shorter and oval, their middle en velnpu is yellowish, and to this is due the very inaccurate figures of and, like the two others, has externally numberless llv:xn hy IVestru7nb a.n. 67;, who has observed the eggs of the Ceatodes ative vesicle, &c. — Kd. <^117. THE HELMINTHES. 125 Thej send off two varicose Vasa deferentia to the posterior portion of the body, where, after uniting very probably with the neck of an odd elongated vesicle (Fe^räiZa 5e/?^^7^a/w ?), they are prolonged into a copula- tory organ/^* There are six pyriforni bodies, which secrete a finely-granu- lar substance, and are- attached behind the testicles to the Vasa dtferentia. Their six excretory ducts successively unite, ending finally in two which open into the copulatory oi'gan/-'' The penis is usually folded inward, but when projecting outwardly, it is a nuiscular, cup-shaped appendage, whose fossa receives the posterior portion of the body of the female during copulation.^"' The spermatic particles are developed after the usual mode ; they are filiform and very active, and quickly die in water, interlooping and twisting together/'^ The very adhesive, viscous, yellowish-brown wax-like substance, often found about the vulva, is apparently the secretion of the pyriform bodies during copulation/^' § in. With the Nematodes, the genital organs consist of a long, simple or partly double caecal tube, which winds around the straight intestine. In the female it has the following parts : Ovarium, Tuba Fallopii, Uterus, and Vagina; and in the male. Testes, Vas deferens, Vesicula seminalis, and Ductus ejaculatorius. With Trichosoma, Trichocephalus, and Spkaerularia, the genital tube is simple in the females, and usually so in the males. But in Filaria, Asca- ris, Strongylus, Spiroptera, Oxyuris, and Anguillula, the ovary. Fallopi- an tube, and uterus, are double.'^' In the females, the ovary is the poste- rior portion of this genital tube, and in its terminal portion are small round 4 With Echinorlnjnchus strumosn.i, these two round testicles are side by side. Having always found the odd, long vesicle empty, I cannot decide whether or not it serves the function of a seminal vesicle. 5 These six pyriform bodies were formerly taken for seminal vesicles ; see Westrumb, de Helminth. Acanthocei)halis, p. 55, Tab. III. fig. 24 ; and ffitzsck, in Ersch and Gruber's Encyclop. VII. 1821, plate for the Acanthocephala, fig. 2, 3, i. ■yVith Ecninorhynchus claviceps, I have found only one of these bodies. ■ (J The copulatory organ, which protruded has mostly an ol)lique direction, has l)etn very exactly figured by IJujardin (Hist. d. Helm. p. 493, PI. VII. fig. D, 1, A, 2). <■ For the spermatic particles of the Acanthoce- phali, see my observations in MüUer's Arch. 1836, p. 232. s This waxy substance incrusts sometimes the whole caudal extremity of females ; this is so with Echinorhynchus gigaa, and slobocaudatux ; see Cloquet (Anat. &c. &c. p. 100, PI. VIII. fig. 4, 5) and Nitzsch (^fViegmann^s Arch. 1837, I. p. 64.* 1 For the simple genital tube with its various parts of the female of Trichocephalus dixpar, see Mayer, Beitr. &c. Taf. II. With Filaria rigida. and Ascaris paucipara, I have found the female organs likewise simple. When these organs are double, either one uterus with its ovary and ovi- duct passes in front from the simple vagina, while the other passes behind, as is the case with Ascaris brevicaudnta, nigrovenosa, Oxyuris vermicu- laris, Spiroptera unthuris, Strongylus auricn- laris, and striatus ; or both pass side by side behind, as in Ascaris aucta, rnystax, lumbri- coides (Cloquet, Anat. &c. PI. I. fig. 2) and aus- culala. With Cucullanus elesans, and micro- cephalus (from the intestine of Emys lularia}, the uterus alone is double ; one horn terminating postei-iorly in a caecum without an ovary or Falla- pian tube, while the other, which has tl'iese pjirts, passes in front. There are, moreover, species of Ascaris into whose vagina open three or four geni- tal tubes. Thus with Ascaris microcephala, I have seen the uterus divide upon reaching the vagina into three tubes, each having an ovary and oviduct. According to Nathusias (fViegm'ann's Arch. 1837, I. p. 57), the uterus or Filaria labiata^ which is at first simjjle, divides at its posterior e.\- tremity into five tubes. Tlie double uterus of Strongylus inflexus has, posteriorly, numerous constrictions, giving it a moniliform aspect. * [§ 116, note 8.] For some further details on the genitalia of the Acanthocephali, see Blanchard (Ann. d. So. Nat. 1849, XII. p. 23), a«d Regne 11# animal nouv. edit. Zoophytes, PI. XXXV. fig. Sb, 3-, 31, 3-, 3'). —Ed. 126 THE HELMINTHES. $117. cells; in the anterior portion, these cells are more numerous and begin to be surrounded by a granular vitelline substance, in which the primitive nucleated cells are still seen; these cells therefore, ought perhaps to be regarded as germinative vesicles. In front, these eggs, which are of a dis- coidal form, are arranged in a row, or are grouped closely around a rachis which traverses the axis of the ovary. In the Fallopian tube, which may be known by its less diameter, the eggs become more mature, and, having been surrounded by a double colorless envelope, pass into the base of the uterus/-' This last is the largest portion of the genital tube, and is dis- tinguished by its well-marked power of peristaltic action. The vagina, which is distinguished from the uterus by its narrowness and its muscular walls, opens at very difiereut points of the body. Grenerally, as for instance in Ascaris, Spirojjtei-a, Strojigylus, Oxyiiris, Cncullamis, and Tri- chocejjhalus, the Vulva, consisting of a transverse fissure, and often sur- rounded by a very remarkable fleshy swelling, is situated either a little in front of, or near the middle of the body ; but sometimes it opens just in front of the anus.'''' The sperm is usually so accumulated in the bottom of the uterus, that this is probably the locality of fecundation.'^' In the males, the posterior portion of this tube is the testicle ; another portion of it, which is short and constricted, is the Vas deferens, which passes into a dilated portion, — the Vesicula seminalis. Usually this last is separated by a constriction from the Ductus ejaculatorius, which opens into another muscular tube (sheath of the penis).''' At the anterior portion of this last, is a horny, copulatory apparatus. The simple or double penis is of variable length, and is protruded by the muscular contractions of its sheath through the external opening, which is always situated at the poste- 2 The fonnation of eggs in various Nematodes has been «lesci'ibeJ by Siebold (BurUach's l*hys- iul. loo. cit. p. 208), by Bagge (Dissert, de. Sti'jn- pylo, &c., fig. 1-5), and KoUiker {MüUer''s Arch. 1843, p. 69, Taf. VI. fig. 20). I have found a rachis in the ovaries of Ascaris aucta, lumbri- coides, mystax, oscu/ata, Cucullanus elegans, and Stronsj/lus inflexus. Tlie eggs of these, while yet immature and flattened, have a point on one of tlieir extremities by which tliey are attached to the racliis. With those of Ascaris liimbricoides, this point is very long during a certain period of develop- ment, and the opposite end lias many deep sulca- tions, giving it a remarkable appearance ; see HenU, iu MuUer's Arch. 1835, p. 602, Taf. XIV. fig. 11. In tlie mature eggs, which are nearly always oval, it is rare that the double colorless envelope can be clearly perceived.. With Trichosoma, and Tri- chocephalus, there is a short diverticulum at each extremity of the egg. But in Ascaris drtitatii, there is at this same place a long fibrillatrd lihuiiriit; see Mayer, Beitr. Taf. II. fig. 8, and KülliUer, in Mailer's Arch. 1843, Taf. VI. fig. 10-18.* •3 Wilh Ascaris dactyluris, CucuUanus ele- gans, Strongylus nodularis, and striatus, the borders of the vulva appear quite swollen. With Trichosoma, this swelling is so attached to the vulva as to resemble a prolapsus of the vagina (^Dujardin, Hist. d. Helm. PI. I.). With Filar ia attenuata, inßexo-caudata, mihi (from the pulmonary cysts of Delphinus pho- caena), and papillosa (see Leblond, Quelques materiaux pour servir ä I'histoire des Filaires et des Strongles, 1836, PI. II. fig. 1), the vulva is at the side of the mouth. With Strongylus paradoxus, it is swollen to the form of a bladder, and is situated near the caudal extremity ; while that of Ascaris paucipara is directly upon the anus. 4 See Bagge, loc. cit. p. 12 ; and Kölliker, in Muller's Arch. 1843, p. 72. 5 For the male genital tube, see Mayer, Beitr. Taf. I., and Cloquet, Anat. &c. PI. I. fig. 5, PI. XI. fig. 8. As yet I have observed only a few exceptions to this typical form with male Nema- todes. With Filaria attenuata, the posterior portion of tlic testicle is liit'urciitr, and with Ascaris vesi- cularis, there are two moderately large caecal pro- longations which arise from the Vesicula semi' nalis at the place where it empties into the fas deferens. * [§ 117, note 2.] Primitively, the ova of Asca- ris consist of nucleolated cells, which are polyhe- dral from mutual pressure. These increase in size gradually, in their passage down towards the ovi- duct, and the granules of the liquid lying between the nucleus or germinative vesicle and the cell-wall become developed into cells, and in this way tha mature ova are formed. Probably no better op- portunity is afforded to perceive that morphologi- cally the ovum is at first only a nucleolated or nucleated cell ; see Leidy, loc. cit. p. 43, PI. VII. fig. 14, c. — Ed. ^117. THE HELMINTIIES 127 rlor portion of the body/"' It has a great variety of forms, and from its sheath arise two antagonistic muscles, which are inserted at its base/'' The spermatic particles, which are always motionless, have usually a cell-form, or, at least, are never filiform corpuscles.® For aiding the union of the sexes during copulation, the males have lobular appendages, papillae, and suckers, situated about the genital opening. Without doubt, the spiral pos- terior extremity also of the animal, is often used for the same purpose. Moreover, in many instances, there is secreted a wax-like substance in- tended to fasten the two sexes too-ether.''-'' 6 According to Leblond (loo. cit. p. 20, PI. III. fig. 1), both the male and female genital openings with Filaria papillosa are quite near the oral ori- fice. I have been unable to confii'm this observa- tion, at least with Filaria attenuata, iiiflexo-cau- data, and another species found in the thoracic cavity of Sturnus vulgaris. T With Trichocephaius, and Trichosoma, the penis is simple and very long, and, beside the mus- cular sheath, has another which is membranous, and sometimes covered with small spines pointing backwards. This sheath, being folded outwards when the penis is protruded, is comparable to a Praeputium ; see Mayer, Beitr. loc. cit. Taf. I., and Dujardin, Hist. d. Helm. PI. I.-III. With nearly all the other Nematodes the penis is double. It is very long with Ascaris acuminata, brevi- caudata, depressa, spiculigera, and Strongylus paradoxus ; but is very short with Ascaris eiisi- caudata, semiteres, Cucul/anus elegans, Fila- ria attenuata, inflexo-caudata, Spiroptera an- thuris, and Strongylus inßexus. With Spirop- tera, the two penises are of unequal length, and with Ascaris paucipara, hrevicaudata,a,n In many Cestodes and Trematodes, the embryos are developed before the eggs are cast, and in some of the last order, they make their escape while the eggs are in the uterus. The development of the Cestodes occurs as follows : After the disap- pearance of the germinative vesicle, large, transparent embryonic cells appear in the midst of the vitellus, which undergoes fissuration. These multiply by division, increasing at the expense of the vitellus, which in the tightly to the vulva of the female in this act, that opening is always at the posterior extremity of the they cannot disengage themselves (Siebold and body. The testicular tubes of Gordius a?«a118. THE helmi>;thes. 129 end they completely replace. When this has taken place, there is a mass of extremely small cells, which, being covered with a delicate epithelium, form a round or oval embryo, upon one extremity of which there are grad- ually formed six small horny hooks/'* The embryos of the Acanthoeephali are perhaps developed in the same manner, but they have only four hooks/'" The Trematodes are developed exactly like the Cestodes, excepting that their oval embryos have usually ciliated epithelium, and there is an oral sucker in place of the hooks/^* Beside this first period of development, or embryonic state, there are other more advanced or larval states, during which many Helminthes have been described and figured as separate species in the science.*"^ Among these maybe especially noticed two forms of the Trematodes — the cylindrical and the cercarian larvae. The first (the germinative tubes of ßaer), form one of the phases of the alternate generation, and have a more or less complete organization. In the cavity of their body, germinative corpuscles are formed; these consist of a vesicular, granular substance^ and resemble eggs neither by their structure nor mode of development. These corpuscles produce larvae of a cylindrical or cercarian form, which, deprived of their tail, are changed into perfect animals which have genital organs; and thus the series of metamorphoses is terminated.*"* S For the embryonic development of Bothrioce- phalus, and Taenia, see Siebotd {Burdack^s Phys. loc. cit. p. 200), Dujardin (Ann. d. So. Nat. X. 18.38, p. 29, PI. I. fig. 10, also XX. 1843, p. 341, PI. XV., and his Hist. d. Helm. PI. IX.- XII.), and KöUiker {Mailer's Arch. 1843, p. 91, Taf. VII. fig. 44-66). The small hooks which the cestoid embryos so actively protrude and retract, somewhat resemble those which are circularly arranged with the adult Taenia.* 4 As yet, with Echinorhynchus gigas alone have I succeeded in liberating the embryos from the egg by compression. The four hooks of these embryos resemble, by their form and position, those of the Cestoid embryos. It does not appear, how- ever, that the embryos of all Echinorhynchus have them ; at least Dujardin has not found them with those of Echinorhynchus transversus, and globocaudatus (Hist. d. Helm. PI. VII.). 5 For the embryonic development of Monosto- mum, and Distomum, see Siel/old (ßurdach''s Phys. loc. cit. p. 206), and KoUiker {MuUer''s Arch. loc. cit. p. 99). The embryos which swim about like Infusoria by means of ciliated epithelium, and which escape the egg while yet in the uterus, have been observed ol Distomum hians, by Meh- lis (Isis 1831, p. 190); of Distomum nodulosu?n and globiporum, by Nordmann and Creplin (Microgr. Beitr. Hft. 2, p. 139, and in Ersch and Gruber's Eucyclop. XXIX. 1837, p. 324) ; of Distomum cygnoides, longicolle, Amphisto- tmnn subclavatum, and Monostomum mutabite, by mysi:\{ (friegmann's Arch. 1835, I. p. 66, Taf. I.). See also Dujardin, in the Ann. d. Sc. Nat. VIII. 1837, p. 303, PI. IX. fig. 3. I have seen the emljryos of Distonnum tereticolle, and A^pido- gaster conchicola,vfiüio\x.t the ciliated epithelium. Those of Distomum. longicolle, cygnotdes, Mon- ostomum. 7nutaOile, and Aspidogaster conchi- cola, have an oral sucker. In this last species,, there is another sucker also, at the posterior ex- tremity of the body {Dujardin, Hist. d. Helm. p. 325). '' In this category are the genera Cercaria,. Histrionella, Bucephalus and others, which a» yet have been founded only upon different specie» of Trematode larvae. The Hehninth described by Leblond (Ann. d. Sc. Nat. VI. 1S36, p. 289, PI. XVI. fig. 3) as Amphistommn ropalo'ides, is on\y a larva of a Tetrarhynchus. The species forming the genus ScoLex are certainly only imperfect Bothriocephalus ; and the Gryporhynchus pu- sillus of Nordmann (Jlicr. Beitr. Hft. I. p. 101,. Taf. VIII. fig. 6, 7), is probably only a young Taenia. There may also be a doubt here, if the Cystici can be considered as real species. It is very jirobable that they are imperfect Ces- todes whose genital organs are to be afterwards- developed, as with Cysticercus fasciolatus, v/hi\& the Rodents in which it lives are devoured by car nivorous animals. Taenia crassicollis is, per- haps, to Cysticercus fasciolaris, what Bothrioce- phalus nodosus is to Bothriocephalus solidus ; see Creplin, Nov. Observ. &c. p. 90. " The cylindric larvae of the Ti ematodes have been termed by Steenstrup (loc. cit. p. 50) nurses (Ammen). They are yet known only as living parasitically upon Mollusks, as for instance, upon Paludina, Lymnaeus, Planorbis, Ancylus, Sue- cinea, Anodonta, and Unio ; also upon Helix pomatia, and Tellina baltica, according to Boia- nus, Baer, Carus, Steenstrup, and myself The cylindric larvae of Bucephalus polymorphus, are very long tubes, varicose here and there, some- times ramifi.ed, and which do not e.xhibit any * f § lis, note 3.] The history of all our best embryological studies shows that the segmentation of the vitellus is the invariable preface to the be- ginning of development with all true ova. In the case of the Cestodes, if, as above mentioned, there is no such process, it is highly probable that such development is not from true eggs but rather from buds, a view which is the more MÄjrthy of attention from the recent developments made by Sie bold with Gyrodactylus ; see below, my note under § 118, note 7. — En. 130 THE HELMINTHES. ^119. § 119. With the Nematodes, of which very many are viviparous, the embryos are developed within the egg in two diiferent ways : Either the embi'yo- movements (Bner, in the Nov. Act. Acad. Lenp. XIII. pt. 2, p. 570, Tab. XXX.). Those of Dis- tomum duptic.atum liave simple, oval, and rigid germinative utricles (Baer, Ibid. p. 558, Tab. XXIX.). Those of Cercaria ephemera, are also very simple, but of a cylindrical form (Siebold, ia Burdach's Ph.ys. loc. cit. p. 187, and Steenstriip, loc. cit. p. 78, Taf. III. fig. 1-6). Those of Cer- f.aria furcata are simple and cylindrical, but very ilong and endowed with quite active peristaltic motions {Baer, loc. cit. p. 626, Tab. XXXI. iig. 6). The curious animal, Leucocliloridium paradox- U7n, consisting of only a cylindi-ical sac with a tail, is only a trematode larva {Cams, in the Nov. Act. Acad. Leop. XVII. pt. 1, p. 85, Tab. VII.). \\ ith the slow-moving, cylindrical, orange-colored nurses of Cercaria ephernera, there may be easily seen a mouth, a pharynx, and a simple ooecal intestine {Siel/old, in Burdach^s Phys. loc. cit. p. 187). Those of Cercaria echinata, are similar, but they have also two short oblique prolongations in front of the obtuse caudal extremity {Baer, loc. cit. p. 629, Tab. 31, fig. 7, and Steenstrup, loc. cit., p. 51, Taf. II. fig. 2-4). The germinative bodies from which Cercaria is developed, have nothing comparable to a chorion or germinative vesicle. Their larvae have always a tail, which is simple (^Cercaria armata, ephemera, Distomum dupli- catum), or bifurcated {Cercaria furcatu), or double {Bucephalus polymorphus). The move- ments of this tail are very slow with Distomum duplicatum, but extremely lively and vortical with Cercaria. With Bucephalus, the two fiU- form tails lengthen and shorten considerably, at the same time jerking all about. When the larvae are developed, they leave the corpuscles and pass into other animals to complete their final metamorphoses. Many Cercariae appear to prefer the larvae of insects whose bodies they en- ter by means of their cephalic hooks. In this way I have seen the Cercaria armata easily enter the larvae of Ephemera, Nemura, and Perla. By the aid of its sting it can perceive the inttrsegmental membrane of these larvae. Frequently it loses its tail in passing through a narrow opening it has made. Immediately upon reaching the cavity of the body of the larva, it is surrounded by a vesicular membrane, in which the sting is rejected, and the animal enters upon its final metamorphosis. But I have a doubt whether it is there cumpleted, for among the numerous similar parasites which I have found in the most different insects whose larvae are aquatic, as oi Libellula. Adrian, Ephemera, and Phryganea, I liave never met with one whose genital organs were in a state of advanced develop- ment. The full development of these organs, the deli- cate contours of whicli may be seen while the par- asites are in the bodies of these animals, is not perhaps attained, until the insects have been swallowed by birds and other animals, — being thereby furnished with more proper conditions for their complete formation. Some Cercarjae lose their tail and are surrounded with a capsule without leaving the Mollusks which are their first habitat. This is prolrably so, be- cause these Mollusks are liable to be eaten by aquatic birds, in whicli these parasites may prop- erly reach their final development. It should, however, be remarked that when these larvae be- come chrysalides, their investing capsule or cyst, is a secretion from their bodies, and not a product of the animals in which they live. It is iirobable that very many of these larvae never attain a per- fect state, for, in their migrations, they fail to reach their destined and final habitat. These migrations undoulrtedly occur with many Cestodes while young ; at least Miescher (loc. cit.) has observed it with Tetrarhynchus. But although we have followed these in their migrations, and the transformation of many of them into Monostomum. and Distomum has been observed, and therefore the completion of their metamorphoses, yet we are but slightly informed as to their beginning by the alternation of generation. There is yet little known as to the manner in which these embryos are changed hito the cylin- dric nurses. There are now only two isolated facts throwing light upon this point. According to my own observations {IViegmami's Arch. 1835, I. p. 75, Taf. I.), each embryo of Monostomum mutatiile contains a germinative tube, which, at the death of the embryo, is freed and quite resem- bles the nurse of Cercaria echinata. I have also observed in the embryos of Amphistomum sub- clavatuvi a tubular body, but I could not satisfy myself of its germinative nature. According to Steenstrup (loc. cit. p. 98), there is an animal like a Paramaecium, and probably an embryo of a Distomum, living in Muscles, and which finally is deprived of its epitljclium, an appear to float from place to place by means of their epithelium, thus really neither creeping nor swimming. 1 With MicTostomum lineare, Örstrd, these prehensile organs so closely resemble those of Hydra that they need not be described. According to Örsled they are urn-shaped glands in the centre of which are parabolic bodies which are constantly in motion (loc. cit. p. 73^ Taf. II. fig. 18). But liad he pressed these organs between two iilates of glass, he would have seen the protruding filament, together with its double hooks. '■i 1 have seen these corpuscles protruding through the lateral border of the body of Planaria lactea. In the dorsal papillae of Thysanozoon Diesingii., a part of tliese corpuscles are contained in cells ; but the others are free and often protrude through the skin. With Mesostonium Ehrenbergii, and rostratum, they are arranged in rows in the anterior half of the body, forming striae, which quickly catch the attention. Ör.ited has taken these corpuscles for as many muscular columns (loc. cit. p. 70, Taf. II. fig. 26, 37). The spines which, according to him (loc. cit. p. 72, Taf. II. fig. 29, 3-1) cover the eutii-e surface of Macrosto?num hystrix, are probably of the same nature, as may also be said of the delicate short bristles found everywhere under the skin of Derostomum leu- cops, Dug:es. Quatrefages, in his monograph on marine Planariae (Ann. d. Sc. Nat. IV. 1845, p. 146, PI. VIII. fig. 9, 10), also mentions various formations wliich, partly as spines, partly as nettling or- gans, are found in the skin of certain Dendrocoeli. 1 The mode of locomotion by which these animals move over solid bodies, or upon the surface of the water, has not yet been satisfactorily explained. The ciliated epithelium cannot here be the principal agent. According to Schulze, loc. cit. p. 32, the staff-like corpuscles projecting from the back of these animals, and which he terms bristles, are used as oars. According to Mertens (Mira, de I'Acad. de St. Petersbourg, 6^""^, sir. II. 1833, p. 5), Planaria lichenoides moves by means of the protruded lobes of its pharyngx. 2 Tor example, Mesostomum. ^§ 123, 124. THE TURBELLARIA. 135 CHAPTERS III. AND IV NERVOUS SYSTEM AND ORGANS OF SENSE. § 123. The nervous system with the Turbellaria, is quite indistinct, for it has not yet been observed in the small species, and in the larger ones its dis- position is yet doubtful. A double ganglion in the cervical region appears to form its central part, and from this nerves pass off in different direc- tions."' § 124. Among the organs of sense, those of vision are the most developed with very many species. The red, brown, or black spots on the anterior extremity, two or more in number, are not always simple pigment cells, *^' but may be regard- ed as eyes, for they have a cornea, — a light-refracting body surrounded with pigment, and a nerve-bulb. ^^' As to the sense of touch, no special tactile organs have yet been found, but the whole surface reacts sensitively from the lightest contact; and this sensibility appears particularly prominent at the anterior extremity, which, with many Dendrocoeli, is furnished with lobular and other appendages. '■'^^ 1 Ehrenbers has seen two disconnected ganglia with Planaria Inctea (Abhand. d. Berl. Akad. 1835, p. 243). With other Dendrocoeli, as with Planocerasar^assico/a, and pellucida, tliese two ganglia are blended into one ; at least, the organ which Mertens has here described as a heart, has exactly the appearance of two united ganglia (loc. cit. Taf. I. fig. 6, Taf. II. fig. 3, m. or Isis 1836, Taf. IX. fig. 3, c. m.). The light pulsations which this author affirms to have here observed, are perhaps, as Ehrenberg has supposed (loc. cit. p. 244:), due to the contractions of neighboring organs. According to Schulze (loc. cit. p. 39), with Planaria torva, the double central ganglion gives off two nerves, which pass backwards on both sides of the intes- tine. This double ganglion, situated in the cervical re- gion, and the nervous filaments which it gives off, have been demonstrated by Quatrefages (loc. cit. p. 172, PI. IV.-VI.). 1 Most commonly there are two eye-dots. With Planocera, and Leptoplana, there arc many which are grouped together, and with Polycelis nigra, the whole anterior part of the body is covered with them. In many small species, they appear to be of a simple pigmentary nature. 2 With Planaria lactea, there is, between the cornea-like bulging of the skin, and a semilunar, pigment layer, a small, conical, transparent body, corresponding exactly to a crystalline lens ; see Khrenberg, loc. cit. p. 243, and Schulze, loc. cit. * [ § 124, note 2.] See also Leidy (Proc. Acad. Nat. Sc. Philad. HI. 1848, p. 248) on the eye-specks of Phagocata gracilis, a sub-genus made by him from Planaria, and Schmidt (Die Rhabdocoglen Strudelwürmer, &c., p. 7, and Neue Beitrüge Zur Naturgesch, der Würmer, &c., p. 11). Both of these observers agree m considering these parts in p. 37. With Monocelis, these organs are very remarkable, being composed of two eyes blended into one, and the simple and spherical ball of the eye is filled, according to Örsted, with a transpa- rent vitreous body, in which two conical crystalline lenses are buried with their apices pointing in- wards (loc. cit. p. 6, 56, Taf. I. fig. 1, 2, and in the text, fig. 10). Örsted has distinctly seen two oi)tic nerves passing laterally to this organ. It is quite remarkable that with one of the three known species, the Monocelis unipunctata, the eye is entirely without pigment. Ehrenberg aftirms that he has observed with Polycelis, many star-like ganglia in the middle of the anterior part of • the body, which are for the long row of eye-dots (loc. cit. p. 24.3). For the eyes of the marine Planariae, see also Quatrefages, loc. cit. p. 178, PI. III. The organ which with Monocoelis has been taken for an eye by Örsted, appears to l>e, according to the re- searches of Frey and Levckart (Beitr. p. 83, Taf. I. fig. 18), an auditory organ. That which Örsted regarded a vitreous body, is an otfilite, and his two crystalline lenses, are two semicircular prolonga- tions attached loop-like to the otolite. Frey and Leuckart are also convinced that Convoluta par- adoxa Orst., has a single auditive capsule, situated on the median line of the cervical region, and con- taining an otolite which floats in a lilac-colored fluid ; see Beitr. loc. cit. p. 82, Taf. I. fig. 17.* 3 There are contractile and antenniform append- question as visual organs. Schmidt hag often failed to find anything like an otolite ; but, on the other hand, has often found with various Derosto- mum a complete visual apparatus. This point, therefore, is still unsettled, unless, as Schmidt in- geniously suggests, it may be that one organ serves the functions of two separate senses. — Ed. 136 THE TURBELLARIA. §125. CHAPTER V. DIGESTIVE APPARATUS. §125. With the two orders of Turbellaria, this apparatus is formed upon very diiferent types. But in both orders, the location of the mouth varies so much, that it serves as the basis of genera, according as it is at the anterior extrem- ity, or a little behind it, — or, at the middle of the belly, or a little behind that also. '^'' ■■-ills of the intestinal canal are always intimately blended with the ])a. . iP the body. With the llhabc, il, the mouth leads to a muscular (Oesophagus, which is either an annular sphincter, or a longer or shorter tube, but which, in no case, can be everted from the mouth. The intestinal canal is a simple cae- cum extending from the oesophagus to the posterior extremity ; but with those species which have the mouth situated more or less posteriorly, it stretches forward as a -""ecum to the anterior portion of the body.^' With the Dendrocoeli the muuth opens into a large throat, containing a protrac- tile and very movable deglutitory organ (^Pharynx). This organ, which can be protruded entirely out of the throat while the animal is eating, is either a tube composed of longitudinal and transverse muscles, or a collection of lobular and ramified tentacles circularly ar- ranged about the mouth. Its base is prolonged into the proper intestine, whose dendritic ramifi- cations extend over the whole body.'-' Scarcely a trace of salivary or hepatic organs have here been found with these animals. ''' ages on the anterior part of the body of Planaria ientaculata, and Eurylcpta cornuta, and upon the neck of Planocera. With the last, they sup- port a part of the eye dots. 1 The mciutlL ;iiiil cylindrical oesophagus of Gy- ratrix henniiji/iroilitiia, and Vortex truncata,a.ve at the ceplialic extremity {Ehrenberg, Abhandl. <1. Berl. Aliad. 1835, p. 178, Taf. I. fig. 2, 3). But the mouth and annular oesophagus of Derosto- mum is situated just back of this extremity, into which, however, the coecal intestine extends. The «esophagus is also annular with Mesostomvm, and Typhloplana. In the first, the mouth is at the middle of the ventral surface ; and in the last, a little behind this point, while the intestine projects <;oecally far into the anterior extremity (Orsted, loc. cit. Taf. II. fig. 26, 31, and Focke, loc. cit. 'laf. XVII.). - The genus Planaria has become famous for its movable organ of deglutition, which, being sepa- rated from the body, still continues for a while to swallow all presented to its mouth (ßaer, loc. cit. p. * [ § 125, note 2.] With Phagocata {Planaria) gracilis, Leidy (Proceed. Acad. Nat. Sc. Phil. III. 1848, p. 248) foimd, insteiwl of a single sucker, twenty-three,ln the full-grown animal. These are all protruded when the animal feeds, but when not in use, are closely packed together within the animal. They all connect separately with portions of the dendritic alimentary cavity. — Ed. 716, Tab. XXXIII. fig. 8-11, and Duges, loc. cit. XV. p. 152, PI. IV. fig. 18, 19). The large and plicated oesophag\is of Planaria tremeltaris, constitutes the transition to the ten- tacular form of the deglutitory organs (Dugis, loc. cit. XV. PI. IV. fig. 20, 21). Fully ramift.'d ten- tacles are found with Planocera sargas.sicola, pefliirida, and Leptoplana lichenoides. When collected in the throat, they present exactly the as- pect of a ramified intestine {Mertens, loc. cit. Taf. I. fig. 2, 3, 6, Taf. II. fig. 3, 4, and the Isis, 1836, Taf. IX. fig. 3, b. 3, c). The ramified intestine of many DendrocoCli has been figured by Baer, Du- gis, and Hertens, in their works already cited.* 3 Focke (loc. cit. p. 196, Taf. XVII. fig. 11, c. f.) is inclined to regard as salivary and hepatic or- gans, two large lateral vessels, and a glandular or- gan which he has discovered near the lesophagus and intestine of Mesostomum Ehrenbergii ; hut he himself admits that this view is not yet well founded.! t [ § 125, note 3.] Will (Müller's Arch. 1848, p. 508) has shown that the brownish layer covering the whole extent of the intestine of Planaria is composed of hepatic glands (Dendrococlum lac- teuin, Planaria torva, and nij^ra). — Ed. § 126. TUE TURBELLARIA. 137 CHAPTERS VI. AND VII. CIRCULATORY AND RESPIRATORY SYSTEMS. §126. As yet, only a very imperfect vascular system has been observed in the parenchyma of these animals. With the Dendrocoeli, there are constantly two principal vessels, extending along each side of the body, which give •off many lateral branches and anastomose together at their two extremi- ties. This system has no central heart-like organ, and the walls of the vessels not being contractile, the circulation is probably effected through the gen- eral contractions of the body.'^' The contained homogeneous and colorless liquid ought therefore to be considered as a nutritive fluid. With the Rhabdocoeli, the disposition is different. In many there are one or two vessels which traverse the body and loop at its extremities, without either giving off branches or diminishing in size. The movement of their colorless liquid is due to isolated vibratile lobules situated here and there in the vessels. This organization reminds one more of an aquiferous than a sanguineous «ystem. ^^^ Special respiratory organs are here wholly absent, if we do not regard as i5uch the aquiferous system just mentioned. There remains, therefore, only the conjecture that the ciliary epithelium upon the entire surface of the body is subservient to a general cutaneous respiration, by constantly bringing the water in contact with the skin. 1 Dusfs has described and figured very com- dal extremity, they approach so near to the cuta- pletely the vascular system of Planaria (loo. cit. neous surface that it is impossible to decide whether Jiy. p 160, PI. v. fig. 1, 2, XXI. p. 85, PI. II. fig. they terminate there by a loop, or open externally. 24,25). The cordiform organ which iV/er It is, however, probable that at cer- tain epochs of their lives, genital organs are developed, and therefore, that they multiply also by eggs.*^^ With both the larger Rhabdocoeli, and the Dendrocoeli, the genital and copulatory organs of both sexes are situated upon one and the same individual, so that they are capable of self-impregnation ; but there is generally a re- ciprocal copulation/*^ This genital apparatus is very complex, and as the contents of its various parts have not yet been subjected to a careful analy- sis, it is not positively certain that the right interpretation of them is given. 1 It is yet undecided whether the subcutaneous cell-like bodies of the DeudrocofcU have any relation to this secretion. 1 Dugis (Ann. d. Sc. Nat. XV. p. 169, PI. V. fig. 15) has observed a voluntary transverse fissuration with IJerosto?nu7n leucops. I have been able to follow the very regular fissuration of Microsto- mum lineare, where each unseparated half of the body began to halve again, and then these four pieces also each divi). — Ed. 140 THE TÜRBELLARIA. ^129. their chorion contains only loosely-arranged vitelline cells, among which there is seen no trace of one or more germinative vesicles. The vitelline cells always contain, beside a finely-granular albuminous substance, around nucleus which has a nucleolus. Both the nucleus and the granular sub- stance are shifted from one side to the other of the cell by the very re- markable peristaltic movements of the cell-membrane. After a time, these movements cease, the cell-membrane disappears, and the contents mix with those of other cells which have been afi'ected in the same way : by these means, little collections of vitelline substance here and there are formed, which increase by the addition of other cells, — and finally are transformed into roundish, nicely-defined embryos which become covered with ciliated epithelium. From this time the embryos do not increase as before by th-e external fusion of cells, but there is a muscular, discoid oesophagus formed upon their periphery, and through this the remaining cells are ingested and assimilated within the anhnal. Still later, the embryo, hitherto spherical, becomes flat and elongated at two opposite points; — ultimately, and upon the appearance of the eye- specks, it assumes exactly the form of the adult Pla^iariae. The size of the young Planariae depends upon the number of embryos developed in the same egg, for the smaller this number, the larger the embryos at the time of their hatching, and vice versa. The cause regulating the number of embryos in an egg is yet un- known.*" ^^^ 1 See my details upon this subject in the Bericht, ueljer die Verhandl. d. Berl. Akad. 18«, p. 83. During the development of Planaria, one can, after a while, ascertain the number of vitelline cells assimilated by fusion and deglutition, by counting their nuclei which are easily seen in the parenchy- ma of the body. According to Focke (loc. cit. p. 201), the eye-specks, and the oesophagus are de- veloped very early in the young Mesostomum EhrenbeTgU ; — a species with which each egg contains a single emln'yo only, and which is devel- oped while the egg is in the uterus. The remarkable movements of the vitelline cells in the eggs of the Planariae, and which I was the first to observe, have since been confirmed by Kol- liker, with Planaria lactea ; see fVief^mann^s Arch. 1846, I. p. 291, Taf. X. I am unable to say whether or not the spontaneous movements observed by quatrefages (loc. cit. p. 169, PI. VII. fig. 6-9) upon the larger portions of the vitellus of Polycelis pallidas while in the oviducts, are of the same na- ture ; this naturalist himself supposes that these portions were the eml)ryos of this Planaria.^ * [ End of ^ 129.] Recent embryological studies have thrown some light upon this point — the alleged plurality of embryos in a- single egg. The so-called egg in these cases is almost undoubtedly an ovarian sac, in which are developed many germs; some of these germs may perish, and the fewness of those remaining would give the appearance of an egg with many germs. — Ed. t [ § 129, note 1.] The development of Planfl- ria has been also observed by Schmidt. Die Rhab- doc. Strudelwürmer, &c., p. lY; by Agassiz (Proc. Amer. Assoc. Advancem. of Sc. 'i"*§> 132, 133. THE ROTATORIA. 143 the annular sulcations of the skin, partial, or over its whole extent, give the body an articulated aspect/-^ Many others have a skin so hard and gtiif, as to be like a carapace/^^ CHAPTER II, MUSCULAR SYSTEM AND LOCOMOTIVE ORGANS. § 132. The muscular system of the Rotatoria is quite distinct in many parts of the body. There can at once be observed, distinctly separated from the general parenchyma, unstriated muscles, of which some are transversely annular, and many others narrow and longitudinal.^^' The first, subcuta- neous and widely separated from each other, are usually upon the borders of the segments of the body. The second, divisible into dorsal, ventral and lateral portions, arise from the internal surface of the skin, and are inserted at the cephalic or opposite extremity.^-' The posterior extremity of those species which move freely, has two stiff points of variable length, which are moved as tentacles by two cylindrical, or clavate, caudal muscles. Some have long, movable bristles or pedicles, by which they row along or move by quick leaps.® § 133. The prominent characteristic of the Rotatoria is the retractile, vibratile apparatus at their cephalic extremity, known as the rotatory organs. By these, they swim freely about, revolving upon their axis, or, when at rest, produce vortex-like motions of the water. The form, number, and arrange- ment of these organs varies much according to the genera, and may be «sed even to characterize families. The rotatory organ is either single, double, or multiple. Often it con- sists of a disc, supported by a pedicle of variable length, upon whose bor- ders are successive rows of regularly-arranged cilia, the motion of which gives the appearance of rotation to the disc itself. This apparent motion 2 With Conochilus, Megalotrocha, Lacinula- cles of Euch/anis triquetra are transversely stri- ria, Brachionus, Noteus, Sr/uamena, Notom- ated like those of the higher animals (Die Infus- mata, and Stephanops, the tail is transversely ionsthierchen, p. 462, Taf. LVII. fisr. 8). marked or articulated. With many species of Hy- 2 For the muscles of the Rotatoria in general, see datina, Rotifer, Philodina, Actinurus, and Eos- Ehrenberg, loc. cit. and his description of the Hy- phora, not only the caudal extremity, but the whole datina senta, in the Abhandl. d. Bed. Akad. 1830, body, is regularly segmented, and capable, espe- p. 47. cially at the posterior extremity, of being intussus- 3 Many Rotatoria use their caudal pincers as a cepted or drawn out, like a telescope. fulcrum when creeping along. Philodina move» 3 A solid carapace, like the shell of Daphnia, is along in a leech-like manner, using its mouth and found with Brachionus, Anuraea, Noteus, Salpi- tail as suckers. Polyarthra has many bundles of na and Eiichlanis. bristles upon the sides of its body, which it uses as 1 The muscles are smooth when at rest, but when oars. Triarthra has under the throat and at the contracted, they appear more or less distinctly pli- posterior extremiiy of the body, long stiff bristles, cated transversely. The assertion of Ehrenberg articulated with the body, and by which these ani- ls therefore remarkable, that the longitudinal mus- mals can leap like a flea. 144 THE ROTATOrJA. ^134, is quite remarkable with those species whose single or double disc is not crenulate, but entire. ''' With those whose organs are more numei-ous, but smaller, this appearance is not observed/-^ With Floscidaria, and Stephaiioceros, the rotatory organs have quite a different form. With the first, there are five or six button-like processes about the mouth, covered with very long bristles ; these bristles produce usually but very feeble motions, and rarely give rise to vortexes. But Ste- phanoceros reminds one much of the Bryozoa, for its rotatory apparatus con- sists of five tentacle-like processes covered with vibratile cilia''*' The rota- tory organs differ, moreover, from the ordinary vibratile cilia of epithelium^ in being under the animal's control, — that is, moved or kept at rest, at will.<^' CHAPTERS III. AND IV NERVOUS SYSTEM AND ORGANS OF SENSE. §134. Notwithstanding the transparency of the Rotatoria, and the distinctness with which their organs are separated from each other, yet their nervous- system has not yet been made out with certainty, for their bodies are so small that their peripheric nerves elude the microscope, and their principal nerves' and ganglia cannot be distinguished from the muscular fasciculi, the liga- ments, and the contractile parenchyma of the body. It appears certain, however, that in all, there is, as a nervous centre, a group of cervical ganglia, from which pass off' threads in various direc- tions.^^' 1 Conochilus, Philodina, and Actinurus. 2 Hydatina, Notommuta, Synchaeta, andZ>ig"- lena. 3 See Ehrenberg, Die Infusionsthierchen, Taf. XLV. 4 According to Ehrenberg, there are, at the base of each ciliuin of the rotatory organs, many striated muscles, which, acting antagonistically, produce the motion (Abliandl. d. Berl. Akad. 1S31, p. Si). But neither Dujardin (Infusoires, loc. cit. p. 579), nor Rymer Jones (Compar. Anat. &c. p. 120), has been able to perceive this apparatus. The contractile parenchyma on which the virbra- tile discs are situated, appears to be destined only for the protrusion and retraction of the rotatory organs.* 1 Ehrenberg, to whom we are Indebted for our chief information upon the nervous system of these animals, first took for a cerebral ganglion the gland- uliform body found upon most Rotatoria, and in; the neck of Hydatina senta, and Notommata col- laris (Abhaudl. d. Bcrl. Akad. 1830, p. 52, Taf. VIII. 1833, p. 189, Taf IX., and. Die Infusionsthier- chen, p. 386, &c.). Besides this ganglion, he has- mentioned with Hydatina, Synchaeta, and Dig- lena, many others scattered through the anterior part of the body, and connecting with the cerebral one by nervous filaments. Likewise, with Enter- oplea, Hydatina, Notommata, and Diglena, he- has regarded as a nervous loop, the two filaments which pass off from the cerebral ganglion, and go to the cervical respirntory orifice. Finally, he refers to the sensitive systi-m, a wliite sacculus, single or double, and situated behind the cerebral ganglion, with Notommata, Diglena, and Theorus (Die Infusionsthierchen, p. 425). GrantKi description of the nervous system of the Hydatina, as being composed of many ganglia and a ventral cord, » [§ 133, note 4.] Dobie (Ann. of Nat. Hist. 1848) speaks of two kinds of cilia with Flo.icu/aria ; " one of the usual short vibratile kind, covering the inte- lior of the alimentary lube ; the other extremely long and filiform, of uniform thickness, and not Vibratile under ordinary circumstances." They ar» slowly moved, being spread out by the contractile substance of the lobes of the rotatory organ. — E». ^S§ 135, 136. THE ROTATORIA. 145 § 135. Beside the sense of touch, apparently located chiefl} in the rotatory organs and their tentaculiform processes/'' these animals have also an organ of vision. Usually this consists of a single or double eye-speck upon the neck ; and sometimes, though rarely, of three or four red specks upon the forehead.^-' These specks are usually very small, but nicely defined, and covered by a kind of cornea. They are situated inniiediately uitou the cerebral ganglion, or are directly connected with it, by nervous tilaments.^'^ CHAPTER y. DIGESTIVE APPARATUS. §136. The digestive apparatus is well developed with the Rotatoria, and has the following parts : The mouth opens into a muscular pharynx which has two horny, masti- catory organs, which move laterally upon each other. Succeeding this pharynx is a narrow oesophagus of variable length, which leads to a stomachal (Outlines, &c., p. 88, fig. 82, B.), is founded, un- doubtedly, upon supposition, and not upon real Ob- servation.* 1 The vibratile disc of Conochilus has upon its centre,four cylindrical processes, terminating usu- ally by a bristle, and quite resembling antennae. The two or faui- styles projecting from the front of Synchaeta, are probably of the same nature. ^ The eye-speck is sunple with Euchlanis, Ifo- tommata, Synchaeta, Cycloglena, and Brachio- nus ; double with Conochilus, Mei^a/otrocha, Dislena, Rotifer, and Philodina ; with Eosphora, there are three, and with Squamella, four ; while Hydatina, Enteroplea, Ptygura, Tubicolaria, and the adult Flosculariae, have none at all. 3 Ehrenberg, who was the first to regard these red dots as eyes, has given their intimate structure in none of his writings ; tins is the more to be * ( § 134, notel.] Gosse (Ann. Nat. Hist. 1850, p. 21) describes the nervous system of Asplanchna priodonta as follows : " Each of the three eyes rests "»n a mass that appears ganglionic ; the clubbed masses at the lateral apertures are probably of the same character ; and the interior of the body con- tains a number of very delicate threads, floating freely in the contained fluid, which have thickened knobs here and there, especially where they anas- tomose." Leydig (Zur Anat. und Entwickelungsgeschichte der Lacinularia socialis, in Siebold and Kölliker's Zeitsch. Feb'y, 1852, p. 457) describes a very pecu liar nervous system with Lacinularia, consisting of : "1. A ganglion behind the pharynx, composed 13 regretted since Dujardin has not regarded them- as visual organs (Infusoires, p. 591). He sup- ports this view by the fact that they disajjpear with the adult individual ; but this objection will appear valueless when it is remembered that this is also true of certain parasitic Crustacea. At all events, the small ocular dots of Conochilus, Rotifer, and Philodina, are nicely-deflned organs surrounded with a solid capsule, and appear to me wholly dif- ferent from the dJfused masses of red pigment which Ehrenberg has erroneously taken for eyes with the Infusoria. The disproportionate size of the red dots which Ehrenberg (Die Infusionsthier- chen, Taf. LI. LIII. LVI.) has figured with Notom- mata forcipata, Synchaeta ballica, Cycloglenay and Eosphora, lead one to sui^pose that they are only collections of jiigmentary granules. of four bipolar cells with their processes. 2. A gan- glion at the beginning of the caudal prolongation, similarly composed of four larger ganglionic cells and their processes." But, that these parts belong to the nervous system, appears by no means posi- tive ; for, as, this observer candidly observes, and it is, I think, a capital comment on this whole class of study : " That these cells, with their radiat- ing processes, are ganglion globules and nerves, is a conclusion drawn simply from the histological constitution of the parts, and from the impossiljility of making anything else out of them, unless in- deed, organs are to be named according to our mere will and pleasure." — Ed. 146 THE ROTATORIA. fi 136. dilatation. This dilatation is continuous into an intestine which opens exter- nally by an anus. The mouth is always between the rotatory organs, so that it receives what is drawn in by their vortical action, — the animal swallowing or re- jecting the particles at will.'^^ The pharyngeal masticatory apparatus is round, and composed of two jaws having one or several teeth, which are brought together laterally by the action of special muscles.'-' Usually these jaws are formed of two knee-shaped divisions [Processus anterior and posterior). The posterior division gives insertion to the masti- catory muscles, but the anterior terminates with a tooth, '■''* or as a multi- dentate apophysis.'^' With some which have this last arrangement,'^' the two jaws are formed of three horny arches, and noted for their stirrup-like form. Two of these arches [Arcus superior and inferior), form the arched portion of the stirrup, pointing inwards, while its base is formed by the third arch [Arcus externus), pointing outwards. The masticatory muscles are inserted upon the inferior arch, and move against each other — the transversely-arranged teeth passing over the other two. With the multidentate Monotrocha, and Zygotrocha, the pharynx rests always in the same locality ; but with the uuidentate Polytrocha, it can move up and down, and even be protruded through the mouth. In this last case, the teeth serve as pincers for the seizure of food. The intestine usually traverses the cavity of the body in a straight line, rarely loop- ing,'*^' and is lined throughout with ciliated epithelium. From the stomachal dilatation to a point near the anus, its walls are very thick. The walls of the stomach and intestine are formed of large cells with a colorless nucleus, and which, as they contain a brownish or greenish granular substance, are of an hepatic nature. With most species, two caeca, rarely more, with thick walls and lined with ciliated epithelium, open on the right and left of the beginning of the stomach. Their walls are also composed of large cells, which, as they differ widely from the hepatic ones by their colorless contents, may perhaps serve the function of salivary glands or pancreas. •'^^ The term liectum has been given to a short and terminal- portion of the intestine, which has thin walls, capable of being widely distended by faeces. Its orifice is excretory not only of the faeces, but also of the contents of the genital organs and of the a(iuiferous system — and may therefore be regarded as a cloacal as well as an anal opening. It is nearly always at the base of the caudal extremity. 1 The tcntaculifm-m, rouitory organs oi Stf.phaiio- size throughout, except the rectum wliich is dilated. ceros, are also used for the seizure of food -^ see Hut it is coiled, esiiecially with those which are £hrenberg, Aliliaudl. d. Berl. Akad. 1832, Taf. enclosed in a carapace, as with Tubicolaria, and XI. fig. 1, e., also, Die lufusionsthierchen, Taf. Melicerta, since here the anus is far in front. XLV. fig. XI. 5. i" These two pancreatic caeca are nearly always '■i For the structure of the teeth, see Ehrenberg, present, being wanting only with some si)ecies of Abhand, d. Herl. Akad. 1831, p. 46, Taf. III. IV. Ichthijdium. With JSutummata clavulata, and '■'j P/f:iiri)lrocha, Furcularia, and many species Diglena lacuKtris, there are, besides these caeca of Tiotiimiiuitu, iunl Diglena. which are long, attached to the stomach many 4 Uydalina, Euchlanis, Salpina, Anuraea, smaller sacs, which are colorless and perhaps of Bracfiionus, and many sijecies of Nolommata, the same nature, iind Ijiglena. With Meealotrocha albo-flavicans, there are a J'/iiloUma, Lacinularia, Melicerta, and also two like caecal ajipetidages entering the base Covockilus. of the stomach, and which are independent of the 6 With Euchlanis, and Brachionvs, the stem- Bhort pancreatic ones of the same locality ; see ach is separated from the intestine by a constric- Elirenbers, Abhandl. d. lierl. Akad. 1S31, Taf. tion, and with I'liiludina, the intestine is of equal 111. and, Die lufusionsthierchen, Taf. L. LIV. ^§ 137, 138. THE ROTATORIA. 147 CHAPTERS VI. AND VII, CIRCULATOKY AND RESPIRATORY SYSTEMS. § 137. As no sanguineous system has yet been found with the Rotatoria, it must be admitted that all the organs are bathed directly by the nutritive liquid which transudes through the intestine. ^^' § 138. The vessels observed with the Rotatoria belong probably to the aquiferous system, which, from its structure and limited distribution, must be regarded as of a respiratory nature. In most species, a straight and riband-like organ is seen upon each side of the body, which contains a stiif, tortuous, vasculi- form canal. At the anterior extremity of these two lateral bands, their canals connect with many short lateral vessels which open into the cavity of the body, — their orifices being furnished each with a very active, vibra- tile lobule.^'' These l