^^ 95, 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 Holothurioidea 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.® 



§ 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, die- 3 See, for the spermatic particles of Astera- 

 charge all theii' viscera through the mouth, can, canthioii, Solaster, and .Echinus (Kblliker^ 

 according to Dalyell (Froriep^s neue Not. No. BeitrSge, loc. cit. fig. 1-4, and Valentin, Monogr, 

 331, p. 1), not only reproduce all these, but also &c. fig. 168), of Holothuria and Synapta 

 can divide spontaneously into two oi' more parts, {fVagner, Icon. zoot. Tab. XXXII. iig. 13, and 

 each of which becomes a complete individual. This Qicatrefages loc. cit. PI. V. fig. 2). Those of sun- 

 multiplication by fissuration occurs also, perhaps, ilar form have been seen in Comatula by Muller 

 with Synapta Duvernea ; see (^uatrefases, loc. (Monatsbericht d. Berl. Akad. 1841, p. 189, or tho 

 cit. p. 26. . Abhandl. of the same, loc. cit. p. 235). Accord- 



2 See the eggs of Comatula Europaea {Mill- ing to Valentin (Repertorium, 1841, p. 301), 

 ler, Abhandl. d. Berl. Akad. 1841, Taf. V. fig. 17), those of Spatangus violaceus have an elongated 

 of Asteracanthion, violaceus (JFagner, Pnidro- body, pointed in front, with a very delicate hair -hke 

 mus, &c., Tab. I. fig. 3, or CarM.? and OiZo, Erlaute- tail. Those of Ophioderma longicauda, and 

 rungstafeln, lift. V. Taf. I. fig. 1), of Echinus livi- Ophiothrix fragilis, according to my own obser- 

 dus and sphaera (Valentin Monogr. &c. fig. 167, vation, have a round body, with an equally deli- 

 169), of Holothuria tabulosa {}Vagner, Icon, cate hair-like tail.* 



zoot. Tab. XXXII. fig. 12), and of Synapta Du- 

 vernaea {Quatrefages, loc. cit. PI. V. fig. 1). 



* [ § 95, note 3.] The spermatic particles of the are wide, and of zoological import. Thus it is 



Echinoderms are developed, like those of the other sometimes round {Asterias, JJrastes), sometimes 



Radiates, in special cells, and like them also have, pyriform {Echinocidaris), and sometimes long- 



I think, invariably a cercaria-form. The diifer- conical (J\Iellita). — Ed. 

 ences in the shape of the head of these particles 



