3OO J. E. WODSEDALEK. 



somatic tissue in both sexes. The final preparation of the paper 

 for publication was postponed on several occasions, not at all 

 because of any uncertainties, since the results were convincing 

 from the start, but rather because each additional survey of the 

 entire problem from new material proved more fascinating and 

 gratifying than those preceding. 



VII. CHROMOSOMES IN SOMATIC CELLS. 



Numerous slides were made of various somatic structures from 

 foetuses of both sexes. The organs most frequently used were 

 the brain, lung, liver, Wolffian body, kidney, and intestine. 

 The larger embryos were cut into pieces all of which were then 

 sectioned. Three small embryos, ranging from ten to fourteen 

 millimeter neck-lengths were sectioned in toto. While splendid 

 mitotic figures and late prophase stages were found in many 

 parts of the embryos the very best cells were found in the brain. 

 In the larger specimens the liver and kidneys showed the most 

 favorable cells. 



The male somatic cells, like the spermatogonia, contain thirty- 

 seven chromosomes, of which thirty-six are the ordinary chromo- 

 somes and one is the accessory element or sex-chromosome (Figs. 

 51 and 52). The female somatic cells, like the oogonia, contain 

 thirty-eight chromosomes, of which thirty-six are the ordinary 

 chromosomes and the other two are the sex-elements (Figs. 49 

 and 50). The sex-chromosomes in each case were as distinguish- 

 able as they are in the germinal cells. Literally thousands of 

 somatic cells were carefully studied in each sex. 



After the chromosomes of the first one hundred of the most 

 favorable male somatic cells were studied and carefully sketched 

 it was found that in ninety-three cases there were thirty-six 

 of the ordinary chromosomes present plus the one accessory. 

 In the other seven cases there were slight discrepancies, usually 

 one or two less. This was in all probability due to unnoticeable 

 overlapping. In two cases there were two extra chromosomes 

 present. This was in all probability due to the fact that two 

 of the chromosomes had divided, since these cells were in the 

 early metaphase stage. This interpretation appears to be correct, 

 since it was found later that occasionally some of the chromo- 



