722 C. E. McCLUNG 



to the very obvious conditions in the formed chromosomes of 

 the metaphase, but more extensive knowledge must come from 

 an intimate analysis of structure, which can only be made when 

 the elements exhibit their finer details within the nuclear mem- 

 brane. What has already been accomplished in this way lends 

 great encouragement to the belief that we may expect to know 

 much more about the structures, relations and functions of the 

 chromosomes than we do at the present time. It may justly be 

 said here that the evidence for persistent individuality afforded 

 by the relations between the second spermatocyte chromosomes 

 and those of the spermatogonia is strengthened and made more 

 exact the further the study is pushed back into the entire history 

 of the chromosomes. 



According to many investigators, the result of the second 

 spermatocyte mitosis is to separate daughter chromatids through 

 an equation division. So far as the chromosomes with median 

 or subterminal fiber attachment are concerned, I am inclined to 

 agree, although it must be admitted that with parasynapsis the 

 opposite might be the case. Chromosomes with terminal fiber 

 attachment, however, show the same relations and behavior as 

 similar ones do in Hippiscus. Figures 64, e, f, show such ele- 

 ments extended in the equatorial plate and they must divide along 

 their length if at all. The evidence in support of this view is 

 stronger in Stenobothrus than elsewhere, for the reason that the 

 position of fiber attachment demonstrably remains constant. 

 If this be the case then in such chromosomes as the one shown in 

 figure 64, e, lying in the equatorial plate, the synaptic ends are 

 also the ones to which the fibers attach. Division must separate 

 daughter chromatids from each other, along the longitudinal 

 split of the chromosomes. Beside this chromosome, in the 

 same complex, appears a rod-shaped chromosome extended in 

 the direction of the spindle axis. This I conceive to have already 

 passed through the changes which its neighbor is just beginning. 

 Under any other assumption it must be that synapsis has taken 

 place at the distal ends of the chromosomes or that fiber attach- 

 ment has shifted after synapsis. The evidence is all in favor of 

 constancy in position of fiber attachment, and actual movement 



