228 MICHAEL F. GUYER. 



gonial stages, particularly as regards counts and study of indi- 

 vidual chromosomes. The chromosomes are small and usually 

 lie in a web of plasma or linin which takes the same dyes the 

 chromosome do themselves. Furthermore, the chromosomes 

 tend so to stick together and so overlie one another as ordinarily 

 to render individual identification uncertain. As far as my 

 preparations are concerned, it would have been impossible to 

 have come to even an approximately accurate conclusion re- 

 garding the number and condition of the chromosomes had I 

 depended on what the spermatogonia of adult fowls exhibit. 

 However, the situation may be alleviated in some measure by 

 using the testes of chick embryos, and I have in large measure 

 resorted to the primordial spermatogonia of such material 

 for my more detailed study, supplementing this also by observa- 

 tions on division stages of embryonic somatic cells, particularly 

 those of the renal tubules. 



Even under the best of circumstances, it was difficult to find 

 clear cut cases showing all the chromosomes in one section and 

 so disposed as to render an unequivocal count possible. Most 

 of my notes read "over 16" or "not over 18." The difficulty 

 in the main was that sometimes two or more chromosomes over- 

 lapped in such a way that it was impossible to say whether the 

 given object should be counted as one or two or possibly three 

 chromosomes. Inasmuch as the chromosomes are not all of 

 the same size, two of the smaller ones closely apposed might easily 

 be mistaken for one of the larger ones. In general in favorable 

 preparations, one could pick out two to four very small ones, 

 two to four relatively large rod-like ones, two strongly curved 

 ones and the rest rod-like ones of intermediate size. 



At the outset it should be said that this finding constantly 

 of a pair of curved elements in the male somatic cells came as a 

 surprise to me. I had carried on my observations so long on the 

 large curved element which is so prominent in the primary 

 spermatocytes that my expectation, in studying the cells of 

 embryonic forms, was of finding this same curved element in 

 the somatic cells of the male, or else of not finding it at all since 

 I have always suspected it of being compound in nature. If my 

 mind were prejudiced, it was decidedly in favor of finding a 



