J2 KRISTINE BONNEVIE. 



(b) Eleven to Fifteen and One Half Hours After Fertilization. 



The change just mentioned, proceeds rapidly, and fifteen and 

 one half hours after fertilization the metaphase of the mitosis has 

 an appearance very much like that of the second maturation 

 division. The 28 chromosomes, having in the prophase passed 

 through a V-shaped stage (chrom. 9, 16, later proph., p. 62), are 

 in the metaphase forming as many terminally attached tetrads, 

 standing stiffly out from the spindle (chrom. 12). 



Most of these tetrads show a considerable thickening of their 

 four elements at their inner end ; and a comparison with later 

 stages of the mitosis makes it probable, that this phenomenon is 

 in some causal connection with a dislocation of the point of 

 attachment to the fibers. (See below, p. 74.) 



In accordance with the rodlike shape of the chromosomes no 

 open rings were found in the early anaphase. The doubleness 

 of the daughter chromosomes is, however, still often indicated 

 by narrow openings between their two branches during the sep- 

 aration of the daughter chromosomes (chrom. 28, earl, anaph., 



P- 6 3)- 



In the later anaphase no longitudinal split was visible in the 



daughter chromosomes. 



These are the main facts observed in the material of Nereis 

 now in my hand. The series of stages is, however, not yet 

 complete, and I therefore prefer to postpone a general discussion 

 of the bearing of my results, until I have had an opportunity of 

 examining the nature of the mitosis also at the end of the germ 

 track, and of comparing the chromosomes of Nereis with those 

 of some other types. 



On this occasion I only wish to draw the conclusions reached 

 through the examination of the maturation and cleavage division 

 in Nereis, and also to point out some questions, the answer 

 to which will be of importance for an understanding of the chro- 

 mosome relations in this species. 



1. As already mentioned, the behavior of the chromosomes 

 in all divisions in question is practically the same. Their point 



