52 R. T. YOUNG 



is a question upon which we have as yet no certain evidence. 

 Until the question of the function of conjugation in Infusoria 

 is cleared up, that regarding the relation of endomixis to par- 

 thenogenesis may perhaps better be held in abeyance. 



CONCLUSIONS 



1. Endomixis in Paramaecium can be experimentally induced, 

 especially by the use of metabolic end products and by increasing 

 the rate of metabolism of the animals themselves. 

 . 2. It is not a lethal process, but may be associated with a 

 temporary depression. 



3. It is more or less cyclical in character and probably has a 

 rejuvenating function. 



4. It is not however a necessary accompaniment of temporary 

 depressions and may not be followed by rejuvenation. Other 

 factors are concerned in determining the division rate. 



5. Its relation to parthenogenesis is not clear. 



