522 THEOPHILUS S. PAINTER 



indicate that a shifting of the cytoplasm was taking place, and 

 the spindle would probably rotate until the proper plane was 

 reached and then the egg would divide. 



In its broader aspect, the present contribution adds just one 

 more bit of evidence to show how very important is the role 

 which the cytoplasm plays in development and how very com- 

 plex it is in its organization. The sea urchin egg, was at first 

 considered as one of the simplest types; it seemed certain that, if 

 it was possible anywhere to reduce certain phases of develop- 

 ment to simple mechanical terms, it could be done here. But 

 a mass of experimental data has gone to prove that, in many 

 respects, this apparently simple egg is fully as highly organized 

 as seemingly complex eggs such as the ascidian, for example. 

 The cytoplasm can no longer be looked upon as so much passive 

 material which the nucleus elaborates during development, but 

 it has a complex organization and a development which may be 

 synchronous with certain changes in the nucleus and the division 

 mechanism, and yet is independent of these. 



