70 



THE ACALEPHAE. 



<^§ 67, 68. 



duction by eggs, and consequently by the means of proper genital organs, 

 has been observed in all the families. 



With the Ctenophora/'-' both sexes are combined in the same individual •, 

 but with the Discophora, the individuals are of ou J sex alone/"'^ 



§ 6T. 



The eggs are spherical, ^. ^ "surrounded 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 suifer 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 erillrcly 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 Will, 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 

 (Beiträge z. Naturgesch. wirbelloser Thiere. lue. 

 cit. Taf. I. fig. A. B.) have figured the eggs of Cy- 

 anea pelagia, and of a Medusa. 



2 The spermatic particles of Eiichari.t and Be- 

 roe consist of a round body, having a delicate and 

 very movable tail {Will, loc. cit. Taf. I. fig. 6, 24). 

 In Cydippe they are similar (Krohn, Froriep^s 

 neue Nut. No. 356, 1841, p. 52). This is likewise 

 true of those of the Discophora ; see Siebold, 

 Beiträge loc. cit. Taf. I. fig. c. (Medusa) ; Kolli- 

 ker, Beiträge loc. cit. Taf. I. fig. 8, 9, 10 ; and 

 Millie Edwards, Ann. d. Sc. Nat. XVI. PI. I. fig. 

 1, d. {Rfiizostomum, Chrysaora and Aequorea) ; 



Wagner, Icon. zoot. Tab. XX.XIII. fig. 20, and 

 Will, Hora; tergest. Tab. II. fig. 12 (Pelagia and 

 Geryonia). 



For the spermatic particles of the Discophora, 

 see a •»• Kölliker in the Neue Schweiz. Denkschr. 

 Vin. p. ..., Taf. II. fig. 18 (Cassiopeia), t 



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 Ersaea,. 

 and which he was inclined to regard as Entozoa, 

 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. J 



* [ § 66, note 3.] Reproduction by flssuration 

 has been observed with the Discophora by Kolli 

 ker (Siebold and Köl/iker''s Zeitsch. IV. p. 325) ; 

 he witnessed this phenomena with Stomobrachium 

 tnirahile. It does not appear, however, that he 

 has observed this process with adult forms ; for he 

 remarks that there is reason to believe that this 

 Stomobrachium is only a young, imperfect form 

 of bis Mesonema coe.rulesrens. — Kd. 



t [§ 67, note 2.] The sjKTmatic parti les of the 

 Acalephae have invariably, I think. ^ cercaria- 



form, like those of the Polyps, and like which, also, 

 they are developed in special daughter-cells. — Ed. 

 X [§ 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. 



