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
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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.

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    duction by eggs, and consequently by the means of proper genital organs, has been observed in all the families. With the Ctenophora,(2) both sexes are combined in the same individual; but with the Discophora, the individuals are of Oi- sex alone.® § 67. The eggs are spherical, _ 1 ''-rounded by an exceedingly thin envelope. The vitellus is of a whitish violet or yellow color, and contains a germina- tive vesicle, and germinative dot.® The spermatic particles, which have generally the form of Cercaria (that is, a head and a filiform tail), are very active, and sulfer no change in water.® In some Siphonophora, they appear to have a linear form, and attain a very great size.® §68. The genital organs are not developed except at the epoch of procrea- tion, and this period is very brief. On this account, their existence has often l 'j escaped the notice of observers. The male and female organs so closely resemble each other, as to color, form and position, that they are easily confounded. They consist either of elongated pouches, or of riband-like bands, which are situated in different parts of the body. In the first case, the sperm and eggs escape through particular excretory canals; in the second, they escape directly outwards from the ovaries or testicles, or pass first through large cavities which com- municate externally. As they have no copulatory organs, the water is the medium of fecunda- tion. In this way the unaffected spermatic particles are brought in direct contact with the eggs. 2 Willy Froriep's neue Not. No. 599, p. 66. 3 Siebold, Froriep's neue Not. No. 1081, 1836, p. 33 * 1 Wagner (Prodrom. loc. cit. Taf. I. fig. 2 ; and Icon. zoot. Tab. XXXIII. fig. 15-17) and Siebold (Beitrage z. Naturgesch. wirbelloser Thiere. loc. cit. Taf. I. fig. A. B.) have figured the eggs of Cy- anea pelagia, and of a Medusa. 2 The spermatic particles of Eucharis and Be- roe consist of a round body, having a delicate and very movable tail (Willy loc. cit. Taf. I. fig. 6, 24). In Cydippe they are similar (Krohriy Froriep's neue Not. No. 356, 1841, p. 52). This is likewise true of those of the Discophora; see Siebold, Beitrage loc. cit. Taf. I. fig. c. (Medusa) ■, Kblli- kery Beitrage loc. cit. Taf. I. fig. 8, 9, 10 ; and Milne Edwards, Ann. d. Sc. Nat. XVI. PI. I. fig. 1, d. (Rhizostomurriy Chrysaora and Aequorea) j Wagner, Icon. zoot. Tab. XXXIII. fig. 20, and Willy Horae tergest. Tab. II. fig. 12 (Pelagia and Geryonia). •• the spermatic particles of the Discophora, see rr(tliiker in the Neue schweiz. Denkschr. VIII. p. Taf. II. fig. 18 (Cassiopeia). f 3 It may be that the stout linear and active bodies, seen by Will (loc. cit. p. 78, 81, Taf. II. fig. 26) in the respiratory cavity, the stomach and the general cavity of the body of Diphyes and Ersaeay and which he was inclined to regard as Entozo i are the spermatic particles of these animals, since they quite resemble those of Alcyonella and Cris- tatella. According to Sars (Faun, littor. &c. p. 38), the spermatic particles of Agalmopsis have a cerca- ria-form. \ * [ § 66, note 3.] Reproduction by fissuration has been observed with the Discophora by Kblli ker (Siebold and Kdlliker's Zeitsch. IV. p. 325) 5 he witnessed this phenomena with Stomobrachium mirabile. It does not appear, however, that he has observed this process with adult forms 5 for he remarks that there is reason to believe that this Stomobrachium is only a young, imperfect form of his Mesonema coerulescens.— Ed. t [§ 67, note 2.] The spermatic particles of the Acalephae have invariably, I think, a cercaria- form, like those of the Polyps, and like which, also, they are developed in special daughter-cells. — Ed. } [§ 67, note 3.] These bodies mentioned by Will as spermatic particles have since been exam- ined by Huxley (loc. cit.), who thinks they are not of this nature, a view which is otherwise probable from the fact that he found no male generative sacs, and also because, as I have shown (see my note after § 46, note 5), these particles with Alcyonella have a cercaria-form. — Ed.