270 



THE BIOLOGY OF STENTOR 



multiplication rate was, if anything, slower. Evidently the sym- 

 biosis is of no particular advantage to stentors under optimal 

 conditions. In any event, rapid division led to decrease in 

 symbionts as the host outpaced the chlorellae. 



Interesting experiments on the artificial development of sym- 

 biosis and exchange of chlorellae were also performed. Animals 

 without symbionts were put in an appropriate culture medium to 

 which was added a brei of crushed cells containing chlorellae. 

 White ciliates would then ingest the liberated symbionts, which 



X ^^ aatoirophjj 



hecame colorless laier 



^, e/idurJn^ Sy/nbiosxs ; 



autoirvphic 



lahile or defeciive Symbiosis 



jD^yJT 



Tjor/nally \ / 



-X no saiisfacwri/ 

 symbiosis 



■Makeup wihhdy^cdLty ^ hat yoocL 

 Symbiosis 



•samajbui Chlorella £rom i gneus 

 ^ rendered capable o£ 



y / \ ° o* / Sipnbiosis 



Symbiosis 



Fig. 74. Exchange of Chlorellae and establishment of artificial 

 symbiosis between Stentor polymorphus, S. igneus, and Para- 

 mecium bursaria, diagramming data of Schulze, 1951. Letters 

 correspond to descriptive paragraphs in text, p. 271, 



