Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett.

  • Karl Theodor Ernst von Siebold
Date:
1854
Catalogue details

Licence: Public Domain Mark

Credit: Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    99/482 (page 95)
    CHAPTER IX. ORGANS OP GENERATION. § 95. Although, most Echinoderms have extraordinary jiowers 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 Holothurioidea alone, perhaps, form the exception.(1) 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.(2) The sperm is always milky, and the spermatic particles which are unaffected by sea-water, are nearly always composed'1 of a round or oval, rigid body, to which is attached a delicate, very active tail.® § 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 Holothuria, which, when captured, dis- charge all then’ viscera through the mouth, can, according to Daly ell (Fr or Up's neue Not. No. 331, p. 1), not only reproduce all these, but also can divide spontaneously into two or more parts, each of which becomes a complete individual. This multiplication by fissuration occurs also, perhaps, with Synapta Duvernea; see Quatrefages, loc. cit. p. 26. 2 See the eggs of Comatula Europaca (Mul- ler, AbhaneU. d. Berl. Akad. 1841, Taf. V. fig. 17), of Asteracantkion, violaceus (Wagner, Prodro- mus, &c., Tab. I. fig. 3, or Carus and Otto, Erlftute- rungstafeln, lift. V. Taf. I. fig. 1), of Echinus livi- dus and sphaera (,Valentin Monogr. &c. fig. 167, 169), of Holothuria talmlosa (Wagner, Icon, zoot. Tab. XXXII. fig. 12), and of Synapta Du- vernaea (Quatrefages, loc. cit. PI. Y. fig. 1). * [ § 95, note 3.] The spermatic particles of the Echinoderms are developed, like those of the other Radiates, in special cells, and like them also have, I think, invariably a cercaria-form. The differ- ences in the shape of the head of these particles 3 See, for the spermatic particles of Aster a- canthion, Solaster. and Echinus (IColliker, Beitrfige, loc. cit. fig. 1-4, and Valentin, Monogr, &c. fig. 168), of Holothuria and Synapta (Wagner, Icon. zoot. Tab. XXXEI. fig. 13, and Quatrefages loc. cit. PI. Y. fig. 2). Those of sim- ilar form have been seen in Comatula by Muller (Monatsbericht d. Berl. Akad. 1841, p. 189, or tho Abhandl. of the same, loc. cit. p. 235). Accord- ing to Valentin (Repertorium, 1841, 301), those of Spatangus violaceus have an elongated body, pointed in front, with a very delicate hair-like tail. Those of Ophioderma longicauda, and Ophiothrix fragilis, according to my own obser- vation, h£ve a round body, with an equally deli- cate hair-like tail.* are wide, and of zoological import. Thus it is sometimes round (Asterias, Urastes), sometimes pyriform (Echinocidaris), and sometimes long- conical (Mellita). — Ed.