150 



THE ROTATORIA. 



^§.141. 



§141. 



.Their embryonic development occurs, as in most invertebrate animals, 

 through a complete segmentation of the vitellus ; and the embryonic cells 

 then appear in the segmented portions. 



The newly -hatched embryo has already rotatory and masticatory organs,, 

 eye-specks, &c., and the general form of the adult animal.t ^'^ 



many species was formerly taken for a penis. But 

 the incorrectness of this view has since been seen, 

 for no one has here observed the copulatory act. 

 According to Ehrenberg, who regards these ani- 

 mals as hermaphrodites, certain parts of the aquif- 

 erous system represent the male organs. He 

 regards the two lateral bauds as testicles, and 

 their inferior extremities as vasa deferentia, while 

 the contractile vesicle is the vesicula seminalis. 

 But these organs contain only an homogeneous 

 aqueous fluid, in which there is at no time anything 

 like spermatic particles ; moreover they are fully 

 developed in the young individuals which then 

 have no trace of female organs. 



It would be wholly anomalous that these ani- 

 mals should constantly secrete sperm during their 

 whole life. One would therefore wholly assent to 

 the doubts of Dujardin (Infusoires, p. 587), upon 

 this view of Ehrenberg, and some contradictions 

 into which this last has fallen upon this subject, 

 have been noticed by Doyire (Ann. d. Sc. Nat. 

 XVII. 18^2, p. 199). Kolliker has also thought 

 this view unfounded, and has sought to remove 

 the doubts by a search after the spermatic parti- 

 cles. He regards as such, with Megalotrocha 

 albo-flavicans, the peculiar trembling bodies which 

 he has seen in the cavity of the body, since they 

 are composed of a pryiform body, to which is 

 attached a movable tail. These bodies he affirms 

 are developed in round cells, often nucleated, and 

 he has often counted ten to twenty in the same 

 individual. As he also asserts to have seen eggs 

 at tliis time in the same individual, this would cer- 

 tainly be a proof of the hermaphroditism of these 



animals {Froriep's neue Not. No. 28, 1843, p, 

 17). But this whole observation is somewhat sus- 

 picious, for Kolliker has very probably confounded 

 the vibratile lobules of the aquiferous system with 

 the spermatic particles, and of which there are four 

 with MegalotroiAa in the anterior extremity. 



The observation of R. JVasner (Isis, 1832, p. 386, 

 Taf. IV. fig. 1, 7) is particularly worthy of atten- 

 tion, for followed out, it might lead to the discovery 

 here of male genital organs. He has described 

 peculiar eggs, found frequently by him with Hy- 

 datina senta, and whose whole surface is covered 

 with very fine, thickly-set hairs. He has regarded 

 these as in their first stages of development, 

 although Ehrenberg (Abhandl. d. Berl. Akad. 

 1835, p. 154, and, Die Infusionsthierchen p. 415), 

 has taken this villous envelope for an alga of the 

 genus Hygrocrocis. But these villous envelopes 

 have always reminded me of the masses of sperm- 

 atic particles in the testicles of leeches and which 

 have been figured by He nie as whitish felt-like 

 globules {MuUer's Arch. 1835, p. 584, Taf. XIV. 

 fig. 6. a). 



[Additional Note.] Kolliker (Neue Schweiz. 

 Denkschr. VIII. Taf. II. fig. 31, a.) having since 

 figured the spermatic particles of Megalotrocha 

 albo-flavicans, my former view that he had con- 

 founded these with vibratile organs, is incorrect.*' 



1 Kolliker was the first to observe the complete 

 segmentation of the eggs, with Megalotrocha 

 {Froriep^s neue Not. loc. cit.). It wholly escaped 

 the observation of Ehrenberg amid his numerous 

 researches upon the eggs of these animals ; see 

 Abhandl. d. Berl. Akad. 1835, p. 152.J 



more than the tail of a spermatozoon." He very 

 justly concludes that they cannot at present be 

 definitely regarded as spermatic particles. — Ed. 



* [ § 140, note 2.] The subject of the form and 

 character of the spermatic particles of the Rotatoria 

 is quite interesting, as it may perhaps throw some 

 light on the position of these animals in the animal 

 kingdom. As yet, however, we have very few 

 observations, and even these are not fully defi- 

 nite. 



Schmidt (Vergleich. Anat. &c. p. 268, note) 

 speaks of the spermatic particles of Euchlanis 

 macrura, as being ceixaria-form. 



Leydig (Siebold and Kölliker^s Zeitsch. III. 

 Hft. 4, p. 471) has given those of Lacinularia as 

 composed of a nuclear body from which radiate 

 many tails, like these particles with the Decapods. 

 See Taf. XVII. fig. 2. — Ed. 



t [End of § 141.] We are indebted to Leydig 

 (Zur Anat. u. Eiitwickelungsgesch. d. Lacinularia 

 Bocialis, ill Siebold and Kölliker's Zeitsch. III. p. 



452) and to Huxley (loc. cit. p. 11-15), for extend-' 

 ing our knowledge in this direction. They have 

 carefully observed the development of Lacinu- 

 laria, and the phases correspond exactly with 

 those of Megalotrocha as described by Kolliker. 

 But beside this ordinary mode, of reproduction, 

 they have observed another which is a sexual and 

 analogous if not identical with what has been 

 observed with some of the lower Crustacea (see 

 infra § 292), — propagation by the so-called hiber- 

 nating eggs. Their observations throw light on the 

 whole of this interesting subject, and have fully 

 confirmed me in my previous conjectures that these 

 " Ova " are only gemmae having their exact repre- 

 sentative in the bud-like eggs of the viviparous 

 Aphides. — Ed. 



1 [ § 141, note 1.] Kölliker''s observation above- 

 mentioned on Megalotrocha, has since been con- 

 firmed by Leydig (Isis, 1848, p. 170) who has 

 observed it likewise with Ifotommata and Euch' 

 lams. — Ed. 



