THE NUCLEI OF UROLEPTUS MOBILIS 



329 



Unlike most of the hypotrichous ciliates in culture, the great 

 majority of Uroleptus individuals continue to Uve after conjuga- 

 tion. Of thirty pairs isolated, no less than fifty-three ex-conju- 

 gants continued to live and to divide. When we consider Bait- 



Figs. 79 and 80 Early stages in the development of the new macronuclei. X 



800. 



sell's ('12) experience with Stjdonychia and my own experience 

 with the heterotrich Blepharisma, in which 100 per cent of the 

 ex-conjugants died, this result is remarkable. Even Paramecium 

 has a much larger post-conjugation mortality. There is no a 

 priori reason why mortality in one genus should be higher than 



