386 On Alternate Generation in Annelids, 



servations, striking differences between the young males 

 or females and the parent stock [le parent, I'individu 

 primitif, la souche] are developed after their separation. 

 He says nothing of the development of the eggs of these 

 individuals [I'individu adventif, la nourrice,* la fiUe] into 

 the parent stock, and simply states the fact of the alter- 

 nate generation, without having actually observed it. 

 Milne Edwards f observed a case more similar to that 

 which Miiller had seen. He found in Myrianida five or 

 six young already quite well developed, the more advanced 

 being nearer the tail : he did not observe the mode of de- 

 velopment ; but by carefully comparing the less with the 

 more advanced, he shows how closely this mode of devel- 

 opment of the different parts corresponds to the develop- 

 ment of the same parts of an embryo from an egg. He 

 also observed that the proliferous individuals were provided 

 with sexual organs, and that they seemed alone capable of 

 reproducing the species from eggs. Sars ij: observed the 

 same phenomenon in the Serpulacea, in Filograna implexa, 

 and shows on what slight grounds Ehrenberg § had based 



* Quatrefages has applied the word nurse (nourrice), as generally used, to denote 

 the individual from which the sexual individuals are developed, in a manner very 

 dillerent from tluit of Steeiistrup. He seems to have misunderstood tlie applica- 

 tion of the "Amrae " of the Germans, and has applied his term "nourrice" to 

 a different stage. He has given to the individuals which the Germans call 

 "Amme," the name of " parent," and has given the name of " nourrice " to the 

 males and females developed from this " parent." This is certainly not the mean- 

 ing of Steenstrup, and of the German writers on alternate generation. For ac- 

 cording to this nomenclature of "Quatrefages," we should call '■^pavtiit" the 

 Strobila, Cercaria, and call "nourrice " (Amme) Aurelia, Distoma, instead of call- 

 ing the former (Strobila and Cercaria) the nurses, as is done by Steenstrup. 

 The name of "parent," also, for the " Amme," is objectionable, as it is contrary 

 to the usual meaning of the word ; and the application of tlie word " nourrice " to 

 males and femahs is certainly not in accordance with our understanding of the 

 meaning of that word. What I have called the ^^ parent stock'' corresponds to the 

 "Amme " of Steenstrup. I have given to the olVspring the name of sexual indi- 

 viduals, or of " males " and "females" simply. 



t Milne Edwards (H.) Ann. d. Sc. Nat., 1844, HI., p. 170. 



t Sars (M.) Fauna litoralis Norvegiic, p. 86. Christiana, 1846. 



(j Ehrenberg (C. G.) Die Akalephen das rothen Meeres, p. 82. Berlin, 1836. 



