212 GEORGE ALFRED BAITSELL 



this so-called life cycle could be prolonged by 'artificial stimula- 

 tion,' though be believed the cycle was real and that the stimuli 

 used had only temporarily sustained the life of the culture in 

 the absence of conjugation. Woodruff's work ('12 b) with Para- 

 maecium aureha has shown that, given suitable conditions, this 

 form can be bred indefinitely and the so-called life cycle entirely 

 eliminated. In his work with Paramaecium caudatum, the same 

 investigator has shown that what appeared to be a typical life 

 cycle in this organism was merely the dying out of the race 

 due to unfavorable culture conditions. In Part I of these studies 

 the writer has shown that fundamental changes can be brought 

 about in the life history of the descendants from the same orig- 

 mal animal by keeping the progeny on different culture media. 

 It appears, then, that the environment plays an important 

 part in determining the length of the so-called life cycle and 

 the character of the life history in the Infusoria. Inasmuch as 

 the experimental work on the hypotrichous Infusoria has given 

 evidence that these animals have a definite life cycle, it was 

 decided to re-investigate the problem and endeavor to discover 

 culture conditions in which these forms will live indefinitely with- 

 out conjugation or artificial stimulation and thus eliminate the 

 so-called life cycle for these hypotrichida as has been done by 

 Woodruff with Paramaecium. Accordingly, the experiments re- 

 corded in this paper were undertaken with the view of finding 

 out the life history of the organisms studied when kept on differ- 

 ent media and under varying culture conditions. In order to 

 accomplish this, a number of cultures containing descendants of 

 the same original individual were run at the same time under 

 various culture conditions and consequently the life history of 

 these cultures gives direct evidence on the effect of these varying 

 conditions on the 'same protoplasm.' It was hoped in beginning 

 the work that the conditions encountered, in some culture or 

 cultures of the organisms studied, would be such as to permit 

 the indefinite existence of the animals, and that the 'life cycle' 

 might be ehminated in these forms. Also, if 'sister cells' kept 

 under other culture conditions, which to begin with appeared 

 to be entirely suitable, died out after passing through what ap- 



