THE INFUSORIA 



66-78 descendant nuclei during conjugation, but they all degenerate 

 except one, which alone forms the sexual nucleus (Fig. 60). 



FIG. 40. 



Reconstruction of a series of sections through a pair of Dendrocometes at the beginning of 

 conjugation. M, the meganucleus. TO points to one of the micronuclei in the process of 

 mitosis. One of the three micronuclei in each individual has not begun to divide, but it is 

 much larger than the micronuclei of individuals that are not conjugating. (Original.) 



In the VORTICELLIDAE there is a further modification of the 

 process. The micronucleus of the female divides twice, to form 



A' 



A A B B 



m -M'm' M 



B 



Fia. 41. 



Diagram I., to illustrate the nuclear 

 changes during conjugation of two Holo- 

 trichans, A and B. M, meganucleus ; TO, 

 micronucleus ; N, migratory nucleus ; S, 

 stationary nucleus ; C, cleavage nucleus ; 

 AT, the meganucleus, and TO', the micro- 

 nucleus of the individuals, A' A', B' B', formed 

 by the first fission after conjugation. 



Fio. 42. 



Diagram II., to illustrate the nuclear 

 changes during the conjugation of a female 

 (A) and a male (J5) Voticella. M, meganucleus ; 

 TO, micronucleus of A and B; S, station- 

 ary sexual nucleus ; N, migratory sexual 

 nucleus ; c, cleavage nucleus ; M', the 

 meganucleus formed by the fusion of three 

 nuclei ; and TO', the micronucleus of the 

 regenerated female A'. 



four nuclei, and of these, three degenerate; the micronucleus of 

 the male, on the other hand, divides three times, to form eight 

 nuclei, of which seven degenerate (Fig. 43). Only one cleavage 



