Races of Paramecium. 



527 



The account just given deals with two races under such nutri- 

 tive conditions that such were slender. A further comparative 

 study of two races was made under such conditions that both 

 were thick and plump. For this study the caudatum group was 



Fig. 20. Characteristic forms and sizes of Li and i when both are extremely 

 plump. Edinger drawing apparatus. X 375. 



again represented by the race Lo, while the aurelia group was 

 represented by the very small race i. To the culture containing 

 both these races a quantity of bread was added ; this induced the 

 animals to become very stout. Twenty-four hours after the intro- 

 duction of the bread a sample was killed, and twenty-five of each 

 of the races were outlined with the projection apparatus, as before. 

 The difference between the two races in form was much more notice- 

 able when the animals were plump, so that measurements were not 

 required to show it. Fig. 20 illustrates very clearly the difference. 



