MICHIGAN ACADEMY OF SCIENCE. 



79 



with Ceratophyllum and other pond weeds. At the time the sample 

 was taken the culture was in a flourishing condition, the individuals 

 multiplying by fission. No conjugation was occurring so far as could 

 be determined. This sample of individuals (which we shall designate 

 throughout as the '*D sample'-) may be considered to represent the 

 normal condition of Paramecia of this vicinity with unselected an- 

 cestry. 



TABLE I. 



Frequency Distribution. Length of Paramecia of Unselected Ancestry. 

 Class Unit = 10 mikrons. 



This distribution is shown graphically in Figure 1. 

 deduced from Table I are as follows: 



The constants 



Fig. 1. Diagram I, showing variation in length in sample of Paramecia from "wild" culture of 

 unknown ancestry. The abscissae give lengths in mikrons and the ordinates frequencies of individuals 



TABLE n. 



Variation Constants for Length of Body in Paramecia of Unselected Ancestry. 



