220 O. C. GLASER. 



Osborn ('04, I. and II.), have also published data that have 

 helped to reopen the old wound. It is again debatable what part 

 amitosis plays in normal cell differentiation, and also whether a 

 direct nuclear division may intervene between mitotic divisions 

 without wrecking the ability of the cell in which it occurs to have 

 progeny capable of further differentiation. In the present paper 

 I intend to discuss the first of these questions on the basis of 

 determinations quantitatively as exact as the nature of the subject 

 and material permit. The technical methods employed in fixa- 

 tion, staining, and sectioning, have been fully described in an 

 earlier paper (Glaser, '05). There also will be found evidence of 

 the adequacy of the methods used. 



Developmental Stages Considered. 



The developmental stages which I have considered for the 

 purposes of this work are those of the cannibal and veliger 

 periods. The highly interesting events of this portion of the life 

 history of Fasciolaria have been described in detail (Glaser, '05) 

 but in order to facilitate the description of both the development 

 of the entoderm and of the nuclear phenomena exhibited by this 

 tissue, it will be necessary to restate briefly the chief facts in the 

 gross embryology. 



The entire development of Fasciolaria is influenced and modi- 

 fied, either directly or indirectly, by the process of cannibalism. 

 This form of embryonic nutrition seems to depend on three 

 things : on the fact that the eggs are laid inside of capsules ; 

 that thousands of them remain unfertilized ; and that the embryos 

 within each egg-case differ markedly in age, in size, and in vigor. 

 Given these circumstances, the most vigorous larvae within each 

 capsule ingest all of the infertile eggs and all of the weaklings. 

 Stages, intended to illustrate typical degrees of cannibalism are 

 shown in the second column of Fig. 9, p. 233. 



Larva I. is the earliest stage used. It shows the mouth 

 between the two bulging external kidneys, and contains under 

 the right one, remnants of the macromeres of the segmentation 

 period. Farther down in the digestive tract lie two of the swal- 

 lowed food-ova. 



Larva II. has ingested fourteen eggs, whereas III. is a fully 



