REPRODUCTION OF THE HYPOTRICHOUS INFUSORIA 



57 



After the epidemic had been present for a few days it became 

 evident that the culture was not thriving as it had been previous- 

 ly. This was shown chiefly in two ways: (1) The fall in the divis- 

 ion rate. At the time of the appearance of conjugation in the 

 stock culture, the animals in the main lines were dividing at an 

 average rate of over three divisions per day. For the ten days 

 following the appearance of the phenomenon the average rate fell 



400 



450 



500 



March 

 1911 



April 



May 



a 



June July 



Diagram 3 Graph giving the life history of Culture Sbhb, showing the average 

 daily rate of division of the four lines of culture again averaged for ten day per- 

 iods. Beef extract culture medium. Point marked X indicates the point at which 

 conjugation appeared in the stock culture. 



to approximately two divisions per day. In the next ten days the 

 rate fell to an average of one division per day and this was followed 

 by the death of the culture on the third day following (diagram 1). 

 This fall in the division rate could be noted not only in the slides 

 constituting the main lines of the culture but also in the stock 

 slides. Soon after the appearance of conjugation the slides of 

 stock in many instances instead of having a large number of in- 

 dividuals present would have only a very few. In some cases all 



