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.

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    Spontaneous transverse fissuration occurs particularly with the Abran- chiati,'1* but has also been observed with the Nemertini,® and Branchiati.® It occurs usually at the middle portion or at the border between the second and third segments of the body. Very often there may be per- ceived at this point, when this process has somewhat advanced, the place where, with the two future individuals, there will be a new fissuration. If the animal has a proboscis, tentacles, or eyes, these organs are developed with the posterior individual before its final separation.® These animals have no trace of genital organs, while this process of divi- sion lasts. The individuals thus produced, re-divide, and this division continues until a certain time of the year. It then ceases, and genital organs being developed, reproduction takes place by eggs. The extreme vulnerability and reproductive power of many Chaetopo- des, give rise to their frequent multiplication by artificial and accidental division. The fragments thus produced are finally developed, and the mu- tilated animal ultimately regains its lost parts.® Some have the power of voluntary division from the least handling of their body,® and these sep- arated parts are probably developed to new individuals. § 163. Most of the Annelides reproduce by sexual organs, and the few Lumbri- cini which, as just observed, multiply by fissuration, have probably, like their allied species, genital organs at certain seasons of the year.11’ The eggs of the Annelides present nothing remarkable; they are always spherical, and have a chorion and thin vitelline membrane containing a finely-granular vitellus with a germinative vesicle and dot.® This 1 Lumbriculus, Na'is, Chaetogaster and Aeolo- soma. 2 See Johnston, in the Mag. of Zool. and Bot. I. 1837, p. 534. 3 With the Nere'ideae. 4 Fissuration with many species of Na'is, has already been noticed by O. F. Muller (Naturgesch. einiger Wurm-Arten des siissen und salzigen Was- sers. Taf. II. &c.). For that of Na'is proboscidea and Chaetogaster diaphanus, see Gruithuisen, Nov. Act. Acad. Nat. Cur. XI. p. 243, Tab. XXXV. fig. 1, 3 *, XIV. p. 412, Tab. XXV. fig. 2. For that of Aeo/osoma, see Orsted in Krdyer's Naturhist. Tidskrift. IV. PI. III. fig. 7 ; and for that of Ne- reis prolifera, see Miiller, Zool. Dan. II. p. 16, Tab. LII. fig. 6. This last species is a very young Nereis. It is probable that many other Branchi- ati multiply in the same way. Quat ref ages (Fro- ricp's neue Not. No. 726,1845, p. 344) has recently recognised a Syllis in Nereis prolifera. Sars (Faun. litt. &c. p. 87, Taf. X. fig. 18, 19) has observed multiplication by transverse division with Filograna implexa, a young animal detach- ing itself from the caudal end of this Serpula. I have observed a like division with a Protula, a genus allied to Serpula. According to Milne Edwards (Ann. d. Sc. Nat. III. 1845, p. 180, PI. XI.) a sin- * [§162, note 4.] See in this connection, Schultze (Ueber die Fortpflanzung durch Theilung bei Na'is proboscidea, in Wiegmann's Arch. 1850, p. 293). He has carefully described this form of multiplica- tion with tills animal, and according to him it is a true fissuration, and not a gemmation, as that of Syllis, described by Frey and Leuckart. See fur- gle individual of Myrianida fasciata, which is al- lied to Phyllodoce, produces six young by as many successively disposed divisions. According to Frey and Leuckart (Bcitr. &c. p. 94, Taf. II. fig. 1), there are with Syllis prolifera also, several young developed simultaneously, one after the other, at the caudal extremity.* 5 See the experiments upon this subject with the Lumbricini by Reaumur, Bonnet, Trembley, and Roesel. Daly ell (Froriep's neue Not. No. 331, 18-10, p. 1) has observed a similar mode of repro- duction with Sabella. 6 This has been observed by Grube, with Polia delineata (Zur Anat. d. Kiememvfirmer, p. 58). Meckclia annulata has also the same property. 1 Aeolosoma. 2 See Wagner, Prod. Ilist. gener. loc. cit. Tab. I. fig. 9,10 (Sanguisuga and Nephelis); Stannius, in Muller's Arch. 1840, Taf. II. fig. 1, 2 (Areni- cola piscatorum) ; Milne Edwards, Ann. d. Sc. Nat. Ill, 1845, PI. V. fig. 2, 3, PI. IX. fig. 43, 44 (Terebella and Protula); and Sars, in Wieg- mann's Arch. 1845, I. Taf. I. fig. 13 (Polynot cir- rata). If the bodies which H. Meckel has figured (Muller's Arch. 1844, p. 481, Taf. XIII, fig. 13- 23) as the eggs of Lumbricus terrestris, are really such, which I think is doubtful, they differ much ther Leuckart, Ueber die ungeschlechtlichte Ver- mehrung bei Na'is proboscidea, in Wiegmann's Arch. 1851, p. 134, Taf. II. fig. I.-III. ; and Krohn, Ueber die Erscheinungen bei der Fortpflanzung von Syllis prolifera und Autolytus prolifer. Ibid. 1852, p. 66. —Ed.