150 



THE ROTATORIA. 



§141. 



§141. 



Their embryonic development occurs, as in most invertebrate animals, 

 through 11 complete segmentation of the vitellus; and the embryonic colls 

 then appear in the segmented portions. 



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

 oye-.s;jecks, &c., and the general form of the adult animal.t ^^* 



iii.vy spctire was foniicrly taken for a penis. But 

 lii ■. i.iojrrcctness of this view lias since been seen, 

 I 'I- no one has here observed the copulatory act. 

 Accn-ding to Ehrrnber^, who regards thesa ani- 

 niais as lierniaphrjclites, certain parts of tlie aquif- 

 erous system represent the male organs, lie 

 rcy.'irds the two lateral ))ands as testicles, and 

 their inferior extremities as vasa deferentia, while 

 the contractile vesicle is the vesicula seminalis. 

 ISut these organs contain only an homogeneous 

 x\. .uj.jus liuid, in wliich there is at no time anything 

 liM- spermatic particles ; moreover they are fully 

 d ;velc)peJ in the young individuals which then 

 h;ivo no trace of female organs. 



It would be wholly anomalous that these ani- 

 nuils should constantly secrete sperm during their 

 whole life. One would therefore wholly assent to 

 tin doubts of Diijardin (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. So. Nat. 

 XVII. 18i2, p. 199). KoUiker has also thought 

 this viqfv unfounded, and has sought to remove 

 the doubts by a search after the spermatic parti- 

 cles, lie regards as such, with Mei^alotrocha 

 albo-^avirans, the peculiar trembling bodies which 

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

 are cmiposed 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 this time in the same individual, this would ccr- 

 tjiinly 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, {or Kiilli/cer has very probal)ly confounded 

 the vibratile lobules of the acjuiferous system with 

 the S])ermatic particles, and of which there are four 

 with Megalotrocha in the anterior extremity. 



The observation of R. Wasner (Isis, 1832, p. 38G, 

 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 Ehrcnberg (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 Henle as whitish felt-like 

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

 fig. 6. a). 



[Additional Note.] KollUcer (Neue Schweiz. 

 Denksohr. 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 KoUiker 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 

 reseai-ches upon the eggs of these animals ; see 

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



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) 

 si>eal<s of the spermatic particles of Euchlanis 

 inacrura, as being cercaria-form. 



Eeydig (Siebold and Kijiliker's Zeitsch. III. 

 lift. 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 Ley dig 

 (Zur Anat. u. Entwickelungsgesch. d. Lacinularia 

 socialis, in Siebold and Kiilliker'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 Kiilliker. 

 But beside this ordinary mode, of reproduction, 

 they have observed another which is a se.xual and 

 analogous if not identical with what has been 

 observed wilh some of the lower Crustacea (see 

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

 nating eggs. Theh- observations throw light on the 

 wliole of this interesting subject, and have fully 

 confirvied me in my previous conjectui-es that these 

 " Ova " are only gemmae having their exact repre- 

 sentative in the bud-like eggs of the viviparous 

 Aphides. — Ed. 



I [ §. 141, note 1.] K<jlliker\s observation above- 

 mentioned on Megalotrocha, has since been con- 

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

 observed it likewise with Notonimata and Euck- 

 lams. — Ed. 



