1/8 RALPH S. LILLIE. 



state of permeability of the egg-membrane to ions, and the meta- 

 bolic changes in the cytoplasm, resulting as these undoubtedly 

 do in the production of ions, must be considered in a complete 

 theory. It should also be borne in mind that potential-differ- 

 ences in the cytoplasm may conceivably originate otherwise than 

 by induction j 1 that this is actually so is indicated by the phe- 

 nomena of artificial asters or asters in enucleated eggs (cf. Mor- 

 gan, Ziegler, Wilson). It seems probable however that in mito- 

 sis induction plays the chief part in the production of radiations ; 

 the formation of the sperm-aster appears to be another instance 

 of the same phenomenon. In either case astral radiations are 

 to be regarded as the visible expression of local differences of 

 electrical potential within the cytoplasm. 



1 The localized production (e. g., as an excretory product) of any electrolyte having 

 ions of decidedly different migration-rates would have this effect ; it would be espe- 

 cially marked in the case of acids (e. g. , lactic acid) on account of the high speed of 

 migration of the hydrogen ion. 



