298 BULLETIN OF THE 



I am not prepared, then, to grant that the " Anstoss " to the processes 

 of cell division proceeds from the nucleus ; nor does it seem to me im- 

 peratively necessary to accept the other horn of the dilemma offered by 

 Hertwig. From purely a priori considerations, one might be inclined to 

 think the initiative lay with the protoplasm, for in that event the divis- 

 ion of a cytode would not demand a special explanation different from 

 that of cell division ; but with the view I have suggested it is perhaps as 

 inappropriate to inquire which takes the initiative as it would be to ask 

 whether the carbon or the oxygen begins the process which residts in the 

 production of heat. 



There is ground for believing that in Limax the whole of the " middle 

 piece " does not enter into the composition of the new nuclei, but that 

 portions of the interzonal fibres remain permanently near the surface of 

 the vitellus. 



The flattened or band-like condition of the spindle I have not seen ; 

 it is probably of rather limited occurrence. I have not been able to dis- 

 cover Hert wig's so-called end-pieces, or, to be more exact, I have not 

 seen the nuclear fibres reach the centre of the sun. This, after all, 

 varies w4th the particular stage of advancement, for practically the rays 

 and spindle fibres in the beginning reach almost to the centre of the 

 aster. It is in the later stages (when, for example, a confluence in the 

 elements of the lateral zones has begun) that I fail to find evidence of 

 the continuation of the fibres beyond the region of the lateral thicken- 

 ings. 



In his preliminary note on the development of Heteropods, Fol ('75*, 

 p. 472) says : " Here also the nuclei disappear before each segmentation, 

 and are replaced by molecular stars." 



In his history of the development of Bombinator igneus, Goette ('75) 

 describes the events which succeed the fecundation of the egg substan- 

 tially as follows. 



After the disintegration of the germinative vesicle there arises, prob- 

 ably near the centre of the yolk, a " vitelline nucleus " (Dotterkern) 

 which is not histologically distinguishable from the surrounding yolk. 

 Between this nucleus and the finely granular substance left behind by the 

 germinative vesicle there is only a chance [i. e. no genetic] relationship 

 (p. 51). Owing to the absence of coarser yolk corpuscles (Dotterplattchen) 

 from this nucleus, and to the dark color of the finely granular substance 

 which takes their place, the outline of the nucleus is visible. It migrates 

 toward the surface of the yolk, whereupon there arises within it a deli- 

 cate round corpuscle, — the first " life-germ " (Lebenskeim). The vitel- 



