24 THEOPHILUS S. PAINTER 



Frequently, in first spermatocyte cells, a chromatoid body is 

 found (labeled chr. in fig. 3, text fig. 4, B and D). It usually 

 lies well out of the spindle, and no attempt has been made to 

 follow its history during maturation. 



SECOND MATURATION DIVISION 



In equatorial plate views all secondary spermatocytes show 

 the presence of 11 chromosomes (figs. 13 and 17); of these the 

 autosomes are all typical bivalent or dumb-bell-shaped elements. 

 The sex-chromosome varies in appearance, depending on whether 

 we are dealing with the X-component (fig. 13) or the Y-component 

 (fig. 17). The X-element usually appears as a quadripartite 

 (fig. 13) and the Y-element as a short rod (fig. 17) sometimes 

 bipartite. 



The history of the second spermatocytes is given in figures 13 

 to 20. In figure 18 we see the X-chromosome as it appears in 

 side views of the spindles, and in figures 16 and 19 we can follow 

 the distribution of this element to the spermatids. It will be 

 noted that each spermatid received a pair of egg-shaped chromo- 

 somes which are joined together. Figure 14 is a polar view of 

 one end of a second spermatocyte spindle (telophase) showing 

 the X-chromosome plus 10 autosomes. 



When the Y-chromosome is present in the spindle (fig. 17), 

 it divides equationally (figs. 15 and 20), each spermatid receiving 

 a Y-element. 



Figures 19 and 20 are two cells, which in the testis lie end to 

 end. They are probably the daughter cells of a single first 

 spermatocyte, as no other cells in a similar stage are close to 

 them. In the one daughter (fig. 19) the X-element is seen 

 dividing and in the other daughter (fig. 20) the Y-chromosome 

 is dividing. 



It seems to have been the common experience of a number 

 of workers on mammalian spermatogenesis that in the second 

 spermatocyte there is a tendency of the chromosomes to fuse in 

 pairs, thus bringing about what has been termed by Guyer 

 'double reduction. ' In my shdes the fact cannot be denied that 

 some of the chromosomes do fuse in a way which is suggestive 



