(■) 11. L. WIEMAN 



TIkmc is a well in;irk(Hl interkinesis stage as has been noted 

 l)y Montgomery and von Winiwarter. Figures 33, 34, 35 and 

 3() repr(>sent typical api)earances at this stage. The nucleus 

 exhibits se\'eral chromatin nucleoli of various sizes. The fact 

 that two of larger ones (figs. 33, 34, Xiyi) are much of the same 

 shape as the chromatin nucleolus of the primary spermatocyte 

 has led me to believe that they are the products of the divided 

 A'}'. The appearance varies in different regions of the seminal 

 tubulins. In figure 35 and 36 for example the resemblance be- 

 tween the chromatin nucleoli of this stage and the earlier pri- 

 mary spermatocyte is not so clear. This is due, I believe, to 

 the fact that the appearance of the interkinesis nucleus varies at 

 different periods. In the early part of the period before the chro- 

 mosomes have gone completely into the resting state one finds 

 a larger number of chromatin masses than in later stages. There- 

 fore if the resting stage of the primary spermatocyte be any 

 kind of a guide, the stage at which the bivalent chromatin nu- 

 cleolus shows most distinctly is the stage at which the ordinary 

 chromosomes have practically disappeared, as in figures 33 

 and 34 which show a remarkable resemblance to figure 7. 



Figures 37, 38 and 39 are late prophases or early anaphases 

 of the secondary spermatocyte in which 12 chromosomes includ- 

 ing an XY element may be seen. In figure 39 the XY is al- 

 most separated into two parts. I have not as yet been able 

 to work out in detail the subsequent division of the secondary 

 spermatocyte. I can only point out w^hat seems to be the ob- 

 vious inference that in this division the XY element breaks at 

 the point of union, the X and Y passing undivided to opposite 

 poles of the spindle, while the remaining chromosomes all divide. 

 The result would be that one-half of the total number of sper- 

 matids would receive 11 chromosomes + X and the other half 

 11 chromosomes + Y. 



II. DISCUSSION 



In 1910 Guyer published an account of the chromosome in 

 human spermatogenesis based on the study of a negro testis, 

 in which he described and figures 22 chromosomes in the sper- 

 matogonial metaphase. 



