

«;§^«irfe 



c^-f^. 



14 b 





*y/^>^ 



14 C 



®, 







15b 



Plate XI 



jVb. /4 Prophase and metaphase of a mouse spleen cell in culture. 

 X 2000 (reduction 7/9). (a) Nucleoli are still present, (b) 5-9 minutes 

 later than (a). The developing poles of the spindle have deeply 

 indented the nuclear membrane, (c) 7-8 minutes later than (a). 



{Continued on opposite page.} 



