FIG. 63. Conjugation and reproduction of Paramecium. The 

 macronucleus has been omitted from all except a. After attachment 

 the micronuclei of each conjugant divides twice (b, c) ; three of the result- 

 ing nuclei degenerate and the other divides again (c, d) ; one of the half- 

 nuclei then passes over to the other cell and there fuses with the one left 

 behind (e, /) ; the animals then separate ; the zygotic nuclei then divide 

 repeatedly (i-rti), some of them transforming into macronuclei ; the 

 cells then reproduce by binary fission until the nuclei are distributed in 

 the usual way ; reproduction then takes place in the ordinary manner. 

 (From Hegner, after Calkins and Cull.) 



