Rates of Growth of Individuals 



23 



Schmalhausen and Syngajewskaja ('25) used a dif- 

 ferent technique, measuring body length upon living 

 individuals. In calculating the mean percentage in- 

 crease of length, each individual was treated separately 

 (figure 10). Large variations of temperature and of 



4 8 12 16 £0 24 



Time after beginning constriction in hours 



Figure 9. Growth in length in Paramecium aurelia. Two clones were 

 used, line IE being identical with line I, but cultivated on a different 

 medium. For each point 120 individuals were fixed and measured. (Data 

 of Erdmann, '20). 



culture medium account for the fact that the duration 

 of a single generation fluctuated between 18 and 60 

 hours. Contrary to the opinion of the investigators, 

 it is improbable that the lengths represent the relative 

 volumes of the individuals, for at the modal time of 

 fission (or duration of a single generation), which was 



