S'X 



^ 



c^ d. 



o 



J 



a 





C^ 



C 



Plate I. Resting cells in tissue cultures 



No. I. (a) Chick osteoblast X 2000 (reduction 7/10.) Within the nuclear 

 membrane is the large nucleolus and the heteropycnotic chromocentres. 

 Above the nucleus is a diffuse centrosphere, beyond which are lipoid granules 

 and mitochondria, (b) The same cell 28 seconds later than (o). Notice the 

 migration of the granule (G) independently of the surrounding inclusions. 



{Continued on opposite page.) 



