226 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Orthopteran cells. The formation of chromosomes in the pro- 

 phase of the first spermatocyte that are already prepared for 

 two divisions would a priori render improbable the interven- 

 tion of a rest stage here ; and the actual observed persistence of 

 the chromosomes, as such, through the telophase of the first 

 spermatocyte and through the modified prophase of the second 

 spermatocyte gives actual proof in support of the view that com- 

 monly prevails regarding the suppression of the second sperma- 

 tocyte rest stage. 



Observations upon numerous species tend to show that the 

 behavior of the chromatin during the period between the two 

 spermatocyte mitoses varies considerably with the species and 

 even within the species itself. The amount of diffusion would, 

 in some measure, seem to be related to the form of the chromo- 

 somes and to vary correspondingly in those individuals where 

 the chromosomes are of diverse forms. Thus, where the ele- 

 ments of the second spermatocyte metaphase appear as short 

 double rods, the amount of diffusion is slight, and the indi- 

 vidual chromosomes may be distinguished throughout the telo- 

 phase of the first spermatocyte ; but in those cases where the 

 members of the mitotic figure are much elongated the diffusion 

 is more extensive and the distinction between elements is made 

 difficult or impossible. Since these two conditions may prevail 

 in the same testis, it is probably only a question as to the ex- 

 tent of elongation on the part of each chromosome. In those 

 cases where the elements become very much extended the ap- 

 pearance of the resting condition would be simulated closely, 

 while, on the contrary, chromosomes consisting of spherical or 

 short cylindrical chromatids would never give a suggestion of 

 such a stage. In this we may find, I think, an explanation for 

 those cases in which a rest stage is described as occurring be- 

 tween the spermatocyte generations. 



VI. SUMMARY. 



1. The secondary spermatogonia are much reduced in size at 

 the end of their divisions and the cytoplasm is very small in 

 amount. The rod-shaped chromosomes number thirty-three, 

 and, of these, one is to be distinguished from its fellows by 

 greater size and slower division. 



2. From the substance of the disintegrated spermatogonia! 



