﻿1903] BEHAVIOR OF THE CHROMOSOMES • 255 



to add to my account of this process already published (Mottier, 

 '97, '98). There are no individualized centrospheres or centro- 

 somes. It may be mentioned further that in the mature spindle 

 the following arrangement of fibers is to be observed: bundles 

 of fibers extend from the chromosomes to the poles, a complex 

 of fibers running uninterruptedly from pole to pole, the central 

 spindle fibers, and those which diverge from the poles toward 

 the plasma-membrane {Jigs. 4, 5, 7). 



During mctakinesis the daughter segments undergo a longi- 

 tudinal fission which is at right angles to the plane of the first 

 longitudinal splitting. In favorable cases, the result of this sec- 

 ond longitudinal fission may be seen just as the daughter segments 

 begin to separate or a little earlier, but as a rule the double 

 nature of the daughter chromosomes is not evident until they 

 have separated somewhat {fig. 5). As the daughter chromo- 

 somes separate, the granddaughter segments remain attached at 

 the polar ends while the opposite ends generally diverge, and 

 the well-known V-shaped structure is the result. In fig. 5 it is 

 clear that the V-shaped daughter chromosomes owe this form to 

 the manner in which they are attached to the spindle and to the 

 longitudinal fission of each daughter segment into grand- 

 daughter chromosomes. The chromosomes at this stage are 

 confusing, because of the distortion of the segments due to the 

 former twisting, and because of the fact that different forms of 

 chromosomes with their various modes of attachment to the 

 spindle occur in the same karyokinetic figure. It should never 

 be forgotten, however, that under the circumstances just 

 described in fig. 5 the daughter chromosomes as they pass 

 toward the poles are not always V's, but frequently straight or 

 nearly straight rods which lie parallel and closely applied to 

 each other {fig, S, the chromosome in the middle). If the 

 chromosomes be fastened to the spindle by the ends, the daugh- 

 ter chromosomes will form V's only when the equatorial ends of 

 tne granddaughter segments diverge. 



In such chromosomes as^f^. 2, c d, e, it is apparent that the 

 retreating daughter chromosomes may be either in the form of 

 a U or V, and that this form will arise as a bending of the seg- 



