Production of Heritable Variations m Protozoa 97 



and this diversity is inherited in ordinary reproduction by 

 fission. The same result has been produced wth several 

 other species of Trypanosoma. 



In Paramecium, as well as in some other infusoria, many 

 attempts have been made to so modify the organisms that 

 they will live under conditions which normally kill them. 



Figure 27. Trypanosoma brucei. 1. Individual from which the 

 kinetonucleus has been removed, by treatment with chemicals. 2. 

 Normal form (the kinetonucleus is the dark body near the lower end). 

 After Werbitzki, from Dobell, 1912. 



All such attempts, if they are successful, involve a change 

 in the animals and the inheritance of this change by the 

 progeny. For since they reproduce every twenty-four hours 

 or oftener, the acclimatization would not last longer than 

 that period, if the progeny returned at once to the original 

 condition. 



Most experiments in acclimatization attempt to accustom 

 the organisms to high temperatures ; or to poisons of various 

 kinds. One sometimes gets, from reading, the impression 

 that it is easy to do this. But most persons who try it are 

 greatly disappointed. The organisms appear quite un- 

 changing; if the experiments are not carried on for a very 

 long time, and the change of conditions made with extreme 



