THE NUCLEI OF UROLEPTUS MOBILIS 



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chromosomes in the nuclei undergoing the third division, and 

 concludes that the reduction must have taken place during the 

 second maturation division. In Uroleptus mobilis, finally, we 

 find a process of reduction conforming to these processes in the 

 other ciliates described. The eight chromosomes of the first 

 maturation mitosis (or the many granules of chromatin in aber- 

 rant types, fig. 40), fuse, after division, to form eight chromosomes 

 of the metaphase of the second maturation division (figs. 54 

 and 55). But these eight chromosomes become partially fused 

 to form four pairs. This phenomenon is similar to that de- 

 scribed by Enriques ('08) as occurring in Chilodon uncinatus; 

 but in Uroleptus the fusion is not complete, the two distinct 

 chromosomes of each pair simply lie in close contact (fig. 55, a). 

 The early anaphase stages of this second division furnish some 

 evidence indicating that the two members of each pair possibly 

 slide apart in opposite directions, so that four single chromosomes 

 finally collect at each pole (fig. 55). 



The observations on chromosomes and reduction in ciliates may 

 be summarized in tabular form as follows : 



As to the number of nuclei participating in the second matura- 

 tion or reducing division, we find many variations. In ciliates 

 having but one micronucleus in the vegetative stages the numer- 



