External Factors and Size 



123 



in figure 36. For Paramecium and Stylonychia the 

 results were quite uniform; the body volume dimin- 

 ished to one-half or less with an increase in tempera- 

 ture of fifteen degrees. 



Allescher ('12) also showed that Paramecia were 

 larger at a lower temperature than at a higher one, 



10 



12 14 16 18 20 22 



Temperature in °C 



24 26 



Figure 36. Effect of temperature upon the main body volumes of three 

 species of ciliates. At the temperature of 15° C. the volumes were taken to be 

 100 per cent. The broken line represents approximately the relative rates of 

 reproduction in the three species. (Data of Popoff, '08; Rautmann, '09). 



though her results were complicated by the added fac- 

 tor of starvation. She found that Stentor (figure 37) 

 was influenced in the same way by temperature as 

 were Paramecium, Frontonia, and Stylonychia. So 

 also was Colpoda (figure 39 below) and, so far as is 

 known, all species of unicellular organisms. 



