CONJDGxYTION IN PARAMECIUM 



229 



gamete the smaller male pronucleus is placed close against 

 the cytostome, the larger female pronucleus occupying a 

 deeper position (fig. 48, J}). Both male and female pro- 

 nuclei elongate and form fibrillated spindles, and then a 

 transference of micronuclear material is effected, the male 

 pronucleus of one gamete passing over and fusing with the 

 female pronucleus of the other, and vice versa. The all- 



Taramecxu-Tn caudatum 



Fig. 49. 



co 



Ipoda 



Diagrams of the course of conjugation in the two infusoria Paramecium caudatum and 

 Colpidium colpoda. The transverse lines represent the different stages into which 

 the process may be divided. The black circles represent persistent nuclei, the 

 empty circles stand for those which disintegrate and disappear. The divisions of the 

 gametes are represented by the ovals enclosing the nuclei at the top of the figure. 

 (After Maupas.) 



important act of conjugation, the transference of nuclear 

 material, has now been effected, and the gametes, which 

 have diminished in size during conjugation, shortly afterwards 

 separate from one another, begin to feed again and recover 

 their original dimensions. Each possesses the original 

 unaltered meganucleus and a rather large micronucleus, now 

 called the Combination nucleus, formed by the union of the 

 male pronucleus of the other gamete with its own female 



