156 GARY N. CALKINS 



four micronuclei, all four of them may undergo the first matura- 

 tion division. Of the eight possible micronuclei thus formed, 

 only two undergo the second maturation division, while six are 

 absorbed. All of the four products of the second maturation 

 division may undergo the third division, and of the eight products 

 of this phase, only two become pronuclei, the other six being 

 absorbed. Finally, in the second division of the amphinucleus, 

 two of the four products form the new micronuclei, one forms the 

 new macronucleus, while one, the sister nucleus of the new 

 macronucleus, is absorbed in the cytoplasm (Calkins, loc. cit., 

 pp. 316-326). 



; The cytological details of encystment are not yet worked out. 

 Anticipating the description of the process, it may be briefly 

 stated here that the macronuclei break up into granules as they 

 do after conjugation, and these granules are absorbed in the 

 cytoplasm. 



One phenomenon, therefore, common to division, conjugation, 

 and encystment, is the absorption of variable quantities of 

 nuclear substance in the cytoplasm. That the physical and 

 chemical consequences of such absorption are connected with the 

 phenomenon of rejuvenescence seems probable. That the rela- 

 tion between the new amphinucleus after conjugation, or the 

 new nuclear complex after encystment, and this reorganized 

 cytoplasm is likewise connected with the phenomenon of rejuve- 

 nescence is equally probable. The nature of such connections 

 and of such relations is a matter of speculation for which we are 

 not yet prepared. 



Columbia University 

 March 4, 1919 



