300 ALLEN. [VOL. I. 



of Verson, Frenzel, Lowit, and others who, since the publica- 

 tion of Ziegler's paper, have called attention to cases of ami- 

 totic division of the nucleus which are certainly not followed 

 either by nuclear degeneration or a cessation of cell multiplica- 

 tion. Altogether there seems to be constantly increasing evi- 

 dence that such a fragmentation does occur in the ova of widely 

 separate groups of animals. 



Wilson ('96), p. 85, believes that the subject requires more 

 study, but says : "There can be no doubt, however, that Flem- 

 ming's hypothesis in a general way represents the truth, and 

 that in the majority of cases amitosis is a secondary process 

 which does not fall in the generative series of cell division." 



Absorption. 



At about the time when the transparent nucleus lies near 

 the periphery of the egg the cytoplasm changes from a granu- 

 lar to a reticular structure. The boundaries between the large 

 cells and those adjacent to them now begin to break down and 

 the protoplasm to blend. This fusion may take place between 

 two large cells or between a growing cell and a germ tissue 

 cell. The former usually occurs first, the large cells near the 

 manubrium fusing and then gradually taking in the germ cells 

 which surround them. The nuclei of the latter are found lying 

 in the protoplasm of the absorbing cell. Both conditions are 

 shown in PI. I, Figs. 6, 7. 



The outline of the syncytium thus formed is very irregular, 

 and parts of the walls of the constituent cells persist for a time, 

 showing where the fusion has occurred (Fig. 7). Doflein ('96), 

 p. 66, states that in Tubularia one large, well-nourished cell 

 controls the absorption, and that as it grows its nucleus also 

 increases in volume, and that the nucleus becomes the func- 

 tional nucleus of the ovum, the other nuclei being gradually 

 absorbed. In Parypha, as already stated, the nuclei of the 

 growing cells disappear at an early stage so that only the 

 nuclei of the smaller cells persist. It thus becomes impos- 

 sible to tell which is the controlling cell. 



Finally the mass of fused cells takes on the typical egg 



