REPRODUCTION OP THE HYPOTRICHOUS INFUSORIA 219 



2. Pleurotricha lanceolata 



The culture work with this hypotrichous infusorian was begun 

 on January 6, 1912, by the isolation of a single specimen from a 

 laboratory hay infusion. This individual was placed on a de- 

 pression slide and some of the regular hay infusion added. The 

 species proved to be one that was well adapted for experimental 

 work of this kind, and the progeny from this individual furnished 



1 



Jan. 

 1912 



6°o June 

 1912 



Sepi 

 1912 



Diagram 4 Graph giving the life history of Pleurotricha lenceolata, Culture 

 Ph, showing the average daily rate of division of the four lines of the culture, 

 again averaged for ten-day periods. Hay infusion culture medium. 



the material for all the cultures of Pleurotricha lanceolata men- 

 tioned in this paper. Three different cultures were under obser- 

 vation and each of these is described in detail in the following 

 sections. 



a. Culture Ph. This daily isolation culture, kept on the hay 

 medium, was started January 9, 1912, and continued until Sep- 

 tember 25, 1912, a period of 259 days, during which time it 



