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
Catalogue details

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.

    154/482 (page 150)
    160 §141. Their embryonic development occurs, as in most invertebrate animals, through a complete segmentation of the vitellus; aud 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 Li incorrectness of this view has since been seen, 1 -r no one lias 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 bands 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, m which there is at no time anything 1:. • spermatic particles j 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 (Infnsoires, p. 587), upon this view of Ehrenberg, and some contradictions into which this last has fallen upon this subject, have been noticed by Doylre (Ann. d. Sc. Nat. XVII. 1842, p. 199). Kblliker 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 albojlavicans, 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 this time in the same individual, this would cer- tainly be a proof of the hermaphroditism of these more than the tail of a spermatozoon.” He very justly concludes that they cannot at present be definitely regarded as spermatic particles. — Ei>. * [ § 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 cercaria-form. Leydig (Siebold and Kolliker'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 Kblliker's Zeitsch. III. p. animals (Fr or tip's neue Not. No. 28, 1843, p. 17). But this whole observation is somewhat sus- picious, for Kblliker has very probably confounded the vibratile lobules of the aquiferous system with the spermatic particles, and of which there are four witli Megalotrocha in the anterior extremity. The observation of R. Wagner (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- dat.ina 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)y 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 {Muller's Arch. 1835, p. 584, Taf. XIV. fig. 6. a). [Additional Note.) Kblliker (Neue Schweiz. Denkschr. VIII. Taf. II. fig. 31, a.) having since figured the spermatic particles of Megalotrocha albo-Jiavicans, my former view that he had con- founded these with vibratile organs, is incorrect.’*' 1 Kblliker 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.]: 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 Kblliker.. 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 u Ova ” are only gemmae having their exact repre- sentative in the bud-like eggs of the viviparous Aphides. — Ed. % [§ 141, note 1.} Kblliker's observation above- mentioned on Megalotrocha, has since been con- firmed by Leydig (Isis, 1848, p. 170) who has observed it likewise with Notommata and Eachr- lanis. — Ed.