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and an amicronucleate race occurred while in this culture. If 

 such was the case, it is reasonable to suppose that the six ami- 

 cronucleate individuals isolated to start the six amicronucleate 

 lines were descended in the 'wild' state from a single animal, 

 and likewise all the micronucleate animals were the progeny of 



Fig. 3 Urostyla grandis. Micronucleate race, line Uc, 4th generation, May 

 14, 1920. 



Fig. 4 Urostyla grandis. Amicronucleate race, line Ud, Sth generation, 

 May 18, 1920. 



a single animal. If so, then it was merely a matter of chance 

 that four micronucleate and six amicronucleate lines were isolated 

 from the 'wild' culture. At all events, it is highly interesting 

 that the Urostyla population of the 'wild' culture exhibited two 

 distinct racial types with respect to their nuclear apparatus. 



