116 GARY N. CALKINS 



During vegetative life the fragmentation of the macronucleus 

 into chromatin spheres gives a much increased surface for the 

 interaction of nucleus and cytoplasm. At the time of division 

 these spheres unite into a single compact nucleus with con- 

 siderable loss of material, analogous perhaps, with that formed 

 previously and this material, in the form, possibly, of nucleo- 

 proteids, may be the activating substance which underlies the 

 regenerative power of the cell. 



Columbia University 

 December, 1910 



