68 KRISTINE BONNEVIE. 



After their separation the daughter chromosomes contract to 

 relatively short and thick rods, in which the longitudinal split 

 is in most cases clearly visible (see p. 63, lat. anaph. of 1st mat. 

 div.). Sometimes the two halves of these chromosomes show a 

 tendency to diverge from each other at their free end (chrom. 31); 

 and once I have found a pair of daughter chromosomes (chrom. 29) 

 in which a double longitudinal split seemed present — the one 

 which is usually visible (separating a from «) and on the 

 inside of the diverging halves of the chromosomes another split 

 at right angles to the first one. 



Such a tetrad-like appearance of the daughter chromosomes is 

 found more often in the telophase (chrom. 35, 36). But I have not 

 been able to decide with certainty, whether or not this appear- 

 ance is due to a mere surface structure. An examination of the 

 following stages, however, makes it very probable that these 

 chromosomes ought to be considered as real tetrads. 



Reviewing the different stages of the first maturation division, 

 we find : 



That the point of attachment of the daughter chromosomes 

 corresponds to a point at (or near) the end of the original tetrad. 



That the plane of division was represented by the longitudinal 

 split of the rings and the V-shaped chromosomes of the early 

 prophase — and 



That the longitudinal split of the daughter chromosomes is 

 identical with the space between the two arms of the V-shaped 

 chromosomes. 



What has been said about the chromosomes of the first matu- 

 ration division may with some modifications be applied also to 

 any of the following divisions up to fifteen and one half hours 

 after fertilization. 1 



The elongated chromosomes are before each division placed 

 horizontally on the (vertical) spindle, and — transiently appear- 

 ing like rings, crosses, E-shaped chromosomes, etc., — they are 

 before the separation of the daughter chromosomes carried into 

 a position parallel to the spindle fibers. 



1 Whether the same type of mitosis may be found throughout the whole life of the 

 animal, I am not yet able to say. 



