STUDIES ON CHROMOSOMES. 22Q 



single, curved element in the male, and a pair of such elements 

 in the female, instead of just the reverse the actuality of which 

 slowly forced its way upon me as I examined more and more 

 preparations. 



Where the chromosomes are sufficiently separated to make one 

 reasonably sure that they were all present without overlapping, 

 I find that I have recorded eighteen, rarely more, as the pre- 

 vailing number. In other cases, the number visible is set down 

 as 16, or in some few cases fifteen and seventeen; but in the latter 

 cases since all of the smaller ones can not be identified, I have 

 felt that it is a reasonable presumption to suppose that eighteen 

 were there but that one or more of the smaller ones have adhered 

 to or been obscured by some of the others. Thus my counts as 

 recorded in one set of observations run as follows: 123 cells with 

 eighteen chromosomes; 73 cells with sixteen chromosomes visible; 

 25 with seventeen chromosomes in evidence; 23 cells with fifteen 

 chromosomes in view. Counts can only be made from polar 

 views of equatorial plate stages. Attempts to determine num- 

 bers from side views were all futile. To add to the confusion 

 in side views the chromosomes do not all divide at the same time 

 so that some of the daughter chromosomes are well along toward 

 the poles while others are still at or near the equator. 



Sometimes instead of the expected number of conventional 

 chromosomes, fewer of the latter are in evidence and the field of 

 the mitotic figure, as seen in polar view, is peppered full of much 

 smaller, deeply staining bodies which appear to be chromatin 

 particles. If one counted each of these a chromosome then the 

 number of chromosomes would sometimes total as many as forty 

 or fifty. I am still at a loss to know whether these are particles 

 of linin or mitochondrial material which take the same dyes the 

 chromosomes do, or whether they are fragmented chromosomes. 

 In favor of the latter view is the fact that occasionally, in lateral 

 views, division figures are to be seen in which these particles lie 

 in the equatorial plate as if ready for individual division. 



The particular interest regarding the chromosomes of the 

 spermatogonia centers about the two curved elements which 

 were so frequently in evidence (photos 1-3, Figs. 70-99). They 

 could frequently be picked out even when the other chromosomes 



