IlS E. G. SPAULDING. 



nuclear division continues. In these solutions the electrolytes 

 present in the egg must diffuse outward. Cleavage therefore 

 depends on the presence of these in the cytoplasm. Likewise a 

 strong tendency to fusion shows itself in blastomeres transferred 

 to these solutions during early cleavage stages ; therefore further 

 cleavage also depends on the presence of electrolytes in the cyto- 

 plasm. This action is due to the ions into which they dis- 

 sociate. ' ' 



If all this is admitted it seems to us quite necessary to admit 

 or infer therefrom that the presence of electrolytes in the eggs 

 means also the presence of osmotic pressure; one cannot exist 

 without the other ; consequently their dissociation is identical 

 with an increase in pressure. This would be in perfect agree- 

 ment with our own theory, but is quite ignored by Lillie. He 

 does, however, recognize with us the necessity of accepting a de- 

 crease and rearrangement of surface tension at cleavage, which he 

 accounts for by a difference of electrical potential between the egg 

 and medium. For " Lippman and Helmholtz have shown that 

 the surface tension is greatest when the electrical potential at the 

 boundary is zero, and decreases as the latter increases, for like 

 electrical charges at the surface oppose the tension and diminish 

 it. From this is evident the importance of electrolytes in seg- 

 mentation ; for the production of a potential difference between 

 the egg and the medium separated by a semipermeable membrane 

 is accompanied only by a migration of ions. Therefore, there are 

 ions within the egg originally, and a potential difference implies 

 that ions of like sign are respectively at the surface and in the 

 interior. This state of affairs is found at cleavage. Observation 

 of the direction of the fibrils in the egg during mitosis agrees 

 with this view, /. c., they correspond with the lines of force.' 

 How is this difference of potential between the surface and the 

 interior established ? The answer is that " during segmentation 

 especially is the chromatin markedly acid, the cytoplasm basic." 

 This means in our opinion that there is chemical organization. 

 " Agreeing with the results of Nernst and Olsen, the chromatin 

 represents a charged body by the action of whose negative 

 charges the anions are repelled toward the periphery, or the 

 poles, and the kations are attracted to the nucleus." A curren 



