460 



LORANDE LOSS WOODRUFF. 



altered temporarily by subjecting Paramecium to a markedly 

 changed environment. 



EXPERIMENTS SERIES IV. 



This series is a brief repetition of Series I., since it comprises 

 a comparison of the periodicity of endomixis both in the same 

 races when bred under varied and constant culture conditions, 

 and in different races bred under varied and constant culture 

 conditions. The cultures employed were A, AE and B which 

 were used in the first series, and also two other cultures, M 

 and W. 



The following table shows a practically perfect synchronism 

 of endomixis in all the races under the different environmental 

 conditions: 



This is exactly the same result which was obtained in the 

 experiments of Series I. In Series I this synchronism was 

 most satisfactorily accounted for by assuming that there was an 

 initial effect on the periodicity by the change of environmental 

 conditions to which all the cultures were subjected at the start. 

 That this assumption was justified is shown by experiment C, 

 Series II (cf. p. 455). However, it is to be noted in the present 

 experiment that there is no apparent initial influence of the 

 changed culture conditions, but this is probably due to the fact 

 that the A, AE, B, M and W cultures had been so long under 

 the same environmental conditions before their respective t2 

 subcultures were branched from them. Consequently the syn- 



