SPERMATOGENESIS IN THE ALBINO RAT 157 



and not real, and that Duesberg's small number and failure to 

 note the accessory are to be explamed on this ground. With still 

 better technique than that obtained so far I am quite confident 

 that it will be possible to procure preparations of rat sperma- 

 togonia in sufficiently large numbers that many counts may be 

 made, although such difficulties as overlapping and a large mass 

 of chromatin will always remain, as well as the strong tendency 

 of the chromosomes to stay close together in metaphase. Guinea- 

 pig testis fixed by 'B-15' and carried through by the technique 

 which I found best for the rat shows a very promising condition 

 of the chromosomes. 



In this connection attention is called to figures 18 to 20. 

 Figure 20 (also 58, a photograph of the same complex) indicates 

 the appearance of the first spermatocyte metaphase plates as seen 

 when the chromosomes are fairly well separated, but either the 

 staining or the fixation has not been delicate enough to differenti- 

 ate the organization of the chromosomes. The cell from which 

 figure 20 was drawn is from a testis fixed by cold Flemming's 

 fluid to which urea had been added. This fixative, while occa- 

 sionally isolating the members of the complex pretty well, has 

 never in my preparations, furnished a cell in which the details of 

 chromosome structure could be determined, even when the stain 

 had been extracted to the limit. Figures 18 and 19 are from 

 different rats fixed in 'B-15,' figure 18 from a section, and figure 

 19 from a smear. The drawings bring out clearly the superiority 

 of this fixation. 



Figure 46 is from still another rat fixed in 'B-15.' It shows the 

 excellent general fixation by that method of treatment. In both 

 young and mature testes Flemming's fluid failed in all stages of 

 spermatogenesis to give as workable material in any respect as 

 that fixed in 'B-15.' 



Double reduction certainly does not occur widely, if at all, in 

 the albino rat. Perhaps still greater refinement in technique will 

 furnish preparations in which reliable counts can be made of 

 second spermatocyte complexes and their telophases. 



An exact correspondence in number of chromosomes in the 

 somatic and spermatogonial cells is net to be expected, in the 



