332 



GARY N. CALKINS 



to stain more intensely. Each elongates to form a chromatin rod, 

 and these arrange themselves in lines running from end to end of 

 the nucleus. This ultimately divides by simple constriction with 

 dumb-bell formation; the two daughter nuclei divide again, and 

 these once again, until eight new macronuclei replace those that 

 were absorbed (figs. 91 to 95). 



Figs. 91 to 95 Stages in the division of macronuclei and micronuclei leading to 

 the formation of the typical nuclear complex of the vegetative forms, 96 to 120 

 hours after separation of the conjugants. X 800. 



The micronuclei also divide during this period until from six 

 to eight are formed. Some of these degenerate, leaving the 

 typical number four to six, in the young individual (figs. 93 to 

 95). 



The formation of the nuclear clefts in the macronuclei of the 

 young individuals involves some processes which strongly sug- 

 gest the entrance of supernumerary micronuclei. This will be 

 left for further investigation, however, and will be dealt with in a 

 separate paper on the formation and significance of the nuclear 

 cleft. 



