Diverse Strains in Protozoa 



57 



Figure 22. Eight diverse families of Paramecium, showing varia- 

 tions. Each row represents a single family, showing the maximum, 

 minimum and intermediate sizes of individuals of the given family. 

 The differences in size within the family are due to differences in 

 growth and environment. The differences in average size between the 

 families are hereditary. 



The numbers show the lengths in microns. The mean length for the 

 entire set together is given by the perpendicular line at 155 microns. 

 The mean size for each family is that of the individual above which is 

 placed a + sign. After Jennings, 1909. 



Hutchison (1913) found that they differ in their resistance 

 to heat, some strains standing a higher temperature than 

 others; the same thing was observed by Jollos (1913). 



