CHROMOSOMES IN MAN 463 



the spindle during the division of the remaining twenty-three. 

 In the second spermatocyte division figures, twenty-three and 

 twenty-four chromosomes are seen, all of which divide; so that 

 one-half of the spermatids receive twenty-three, and the other 

 half, twenty-four. 



The difficulties of the problem of the chromosomes in man have 

 not been lessened in any degree by the methods of attack. Thus 

 the conclusions noted above were for the most part based on find- 

 ings in the germ cells of the testis; while the other aspects of the 

 problem, namely, that of the chromosomes in somatic mitoses, 

 has been entirely neglected. It would appear that attempts 

 at corroborating such conclusions by examination of somatic 

 cells have proved unsatisfactory, and in most cases the somatic 

 number has been arrived at by determining the number in the 

 spermatogonia, or by multiplying the number observed in the 

 maturation spindles by two. 



For the purpose of testing the reliability of this method as a 

 criterion for determining the number of chromosomes in the soma- 

 tic cells, as well as learning by direct observation something about 

 the mitoses in these cells, I undertook the present study. This 

 was made possible by the acquisition of unusually favorable 

 material in the form of an apparently normal human embryo 

 (white) measuring 9 mm. from crown to rump, which was fixed 

 shortly after expulsion in an acetic-bichromate mixture, and cut 

 in paraffinin to sections of 10^ thickness.- The sections were 

 stained on the shde with Delafield hematoxylin and orange G, 

 according to the method described by Morris ('09). This stain- 

 ing procedure proved an excellent one not only for general embryo- 

 logical study, but for cytological as well, the chromosomes in 

 many cases standing out with the sharpness of iron-alum-hema- 

 toxylin preparations. 



"For this embryo I am indebted to Dr. H. L. Woodward of Cincinnati, who 

 obtained it from a case of abortion. 



