PANDORINA 



179 



first and simpler method is by continued binary division 

 of all the units composing the colony. Each cell divides into 



Fig. 38- 



Pandorina monan. A, a colony of sixteen flagellated 

 cells enclosed in a common colonial envelope. .5, 

 a colony in which the cells have given rise by 

 repeated binary division to daughter colonies, still 

 enclosed in the common colonial envelope ; cv, 

 contractile vacuole ; si, stigma ; mc, nucleus ; en, 

 colonial envelope. (After Stein.) 



two, the two into four, the four into eight, and the eight into 

 sixteen. The colonial envelope is gelatinised and finally 



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