REPRODUCTION 



155 



Fig. 77. Diagram illustrating the conjugation of Paramecium caudatum. 

 a-q, X about 130 (Calkins); r, a synkaryon, X1200 (Dehorne). 



there are two classes of individuals with respect to "sexual" differ- 

 entiation and that the members of different classes conjugate with 

 each other, while the members of each class do not. These classes 



