and the Embryology of Autolytns cornutvs. 385 



same genus, it was evident that this mode of reproduction 

 was not confined to the Naidina, and that we might ex- 

 pect to find it in other families of Annelids as well as in 

 the two in which it had been observed. The peculiar 

 phenomena preceding the separation of the sexual indi- 

 viduals, the fact that the eggs and spermatozoa seemed to 

 be developed only in the part which was to form a new 

 individual, soon suggested the idea that we might have 

 here a phenomenon, similar to that of alternate genera- 

 tion, taking place among the Annelids. 



Miiller* had observed that the individuals about to sepa- 

 rate were alone filled with eggs, and that these eggs were 

 less advanced in those sexual individuals which were 

 farther from the posterior extremity. He also says, that 

 he found as many as three proliferous individuals placed 

 like links in a chain, one behind the other, the smallest 

 (the youngest) being placed nearest the anterior extremity. 

 Quatrefagesf found on the coast of Bretagne a species of 

 Syllis which reproduced itself by division, producing, how- 

 ever, only a single individual, either a male or a female, 

 and he observed that the anterior part never showed the 

 slightest trace of either male or female organs. This led 

 him to suppose that the individuals which became de- 

 tached were alone capable of sexual reproduction. It is not 

 until several years afterwards, when he returns to the same 

 subject J, and publishes more in detail his observations, 

 that he comes to the conclusion that these phenomena of 

 reproduction by division may be satisfactorily explained 

 as cases of alternate generation. According to his ob- 



* Miiller (0. F.) ZooloRia Danica II., PI. 52, fig. 5-9, p. 15. Havnias, 1788. 

 Copied Ency. Method. (Vers. Vol. I., PI. 56, fig. 12-15.) 



t H. Milne Edwards, Rapports sur une s(5rie de M^moires de M. A. de Quatre- 

 fages, relatifs a rorganisation des animaux sans vert^bres. Comptes Rendus, 16 

 Janv. 1844. Ann. des Scien. Nat. 1844, I., p. 22. 



t A. de Quatrefages, Meraoire sur la generation alteruante des Syllis. Ann. des 

 Sc. Nat. 1854, U., p. 142, PL IV., fig. 3-15. 



JOURNAL B. S. N. H. 49 •'^''^' ^^^^^ 



