508 BULLETIN OF THE 



pronucleus that their morphological equivalency cannot for a moment 

 be doubted. For Clepsine, however, Whitman speaks with the greatest 

 positiveness that " the central area does not disappear, nor even dimin- 

 ish in size," though it is granted that the corpuscles increase a little in 

 their dimensions. 



The chemical behavior of these corpuscles, even in the case of Clep- 

 sine, does not appear to me to be inconsistent with their nuclear nature ; 

 at least, that they are " more deeply colored than the nucleoplasm" is 

 entirely consistent with an interpretation which makes of the " nucleo- 

 plasm" yolk-protoplasm, and of the corpuscles, nuclei, since, as is known, 

 nuclei stain more vigorously than the surrounding protoplasm of the yolk. 



The destiny of these bodies is to coalesce and then to participate in 

 the formation of the spindle. But their smallness in Clepsine seems to 

 preclude the idea of the spindle being formed exclusively, or even 

 largely, at their expense, whereas the size and elongation of the " nu- 

 cleoplasmic " area is such as to produce a conviction that the spindle is 

 formed by the metamorphosis of the latter. Add to this the fact ob- 

 served by Whitman, that this nucleoplasm exhibits the same reaction 

 under treatment with osmic acid as the contents of the germinal vesi- 

 cle, and we have the strongest points that can be made in favor of 

 Whitman's interpretation. I shall not attempt to deny that both 

 " central area " and spindle in Clepsine are largely due to a metamor- 

 phosis of this segregated plasm which Whitman calls "nucleoplasm"; 

 on the contrary, I think we have good reason to believe that the same 

 is true, though to a less extent, in the case of Limax (compare Fig. 85) ; 

 that is to say, that in Limax also the two central areas arise outside of 

 (though not necessarily quite independently of) the two unfused bodies 

 which Whitman calls pronucleoli, and that they and the spindle owe 

 their origin in part to protoplasm which lies quite beyond the limit of 

 those two bodies. The only essential difference in the two cases will be 

 this : that, while in Limax all the nuclear substance (nucleoplasm) is 

 ultimately segregated to form a large nuclear structure, in Cle'psiue the 

 other events of the metamorphosis overtake, as it were, this segregating 

 process while enough nuclear substance still remains diffused in the 

 neighboring protoplasm of the yolk to give the observed reactions under 

 the influence of osmic acid.* But admitting the possibility of the exist- 



* I wish to emphasize at this point the observation previously quoted from Whit- 

 man, — that "the nucleoplasm is more strongly colored in the centre, around the pro- 

 nucleolar bodies, than at the edges," — for, in my opinion, this is evidence that his 

 so-called nucleus is not uniformly nuclear substance (nucleoplasm), but only proto- 



