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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    except upon the belt-like parts of the two extremities. The future ante- rior extremity is directed in front during the motions of the animal, and eyes appear upon it; while the other extremity is gradually divided into segments upon which bristles and feet appear.® While the embryos are thus acquiring the adult form, there appear upon the cephalic extremity and upon the sides of the body, tentacles, cirri, and branchiae, of forms which vary according to families, genera and species. The development of the digestive and circulatory organs occurs also with equal pace,®' 2 See Lovdn in Wiesmann's Arch. 1842, I. p. 302, Taf. VII. (Nereis); Sars, Ibid. 1845, I. p. 12, Taf I. fig. 1-21. (Polynoe); Orsted, Ibid, p. 20. Taf. II. (Exogone); and Milne Edwards, Ann. d. Sc. Nat. ill. 1845, p. 145, PI. V.-IX., or, Froricp's neue Not. No. 721, p. 257 (Tere- belia, Protula, and Nereis). Kblliker (in MS. already cited) has also observed the development of an Exogone, and of a Cyst onere is, an allied ge- nus. Here the embryo is not formed through a complete and uniform segmentation of the vitellus, but, as with the Ilirudinei, the formation is preced- ed by an irregular division of that portion to be the ventral and nervous parts. lie, at the same time, calls the attention to a figure of Milne Edwards, representing the development of Protula, from which it would appear that other Branchiati also are developed like the Ilirudinei; see Ann. d. Sc. Nat. loc. cit. PI. IX. fig. 47.* 3 One ought therefore to be careful about form- ing distinct genera from these larval Branchiati. Thus, Sabellina brachycera, described by Du- jardin (Ann. d. Sc. Nat. XI. 1839, p. 291, PI. VII. * [ § 169, note 2.] For the embryology of Poly- noa, see Desor, loc. cit. p. 12. It agrees closely with that of Nemeries; see also Max Muller, in Muller's Arch. 1851, p. 323. — Ed. fig. 6), is only a larval Terebella, as will be seen by referring to Milne Edwards' figures of the de- velopment of Terebella nebulosa (Ann. d. Sc. Nat. loc. cit. PI. VII. fig. 24, 25). Anisomelus luteus, of Templeton (Transact. Zool. Soc. II. 1841, p. 27, PI. XV. fig. 9-14), is perhaps only a young Serpula. The absence of branchiae and blood-vessels which Qu at ref ages has noticed with many small Branchiati of which he has made new genera (as Aphlebine, and Doyeria, &c.), would lead one to suspect that they are only larvae ; see Ann. d. Sc. Nat. 1.1844, p. 18, or Froriep's neue Not. No. 726, p. 341. H. Koch (see (ibove, § 168, note 5) has lately observed that the young individuals found in the body of Eunice are identical with the Lumbrinereis of De Blainville. The new animal described bv Muller and Busch (Miiller's Arch. 1846, p. 104, Taf. V. fig. 3-5, and 1847, p. 187, Taf. VIII. fig. 1-3) under the name of Mesotrocha sexoculata, appears likewise to be only a young larva of an Annelid. + f [ § 169, note 3.] See Quatrefagcs (Sur l’Em- bryogenie des Ann61ides, in Aim. d. Sc. Nat. X- 1848, p. 153). - Ed.