PLATE 3 



EXPLANATION OF FIGURES 



13 Equatorial plate view of dividing second spermatocyte. Note the quadri- 

 partite form of the X-chromosome. Eleven chromosomes present in this spindle. 



14 End view of late telophase stage, showing chromosomes at one end of 

 the spindle. Eleven chromosomes are seen, including the bilobed X-chromosome. 



15 Late anaphase of second spermatocytic division showing the Y-chromo- 

 some at each pole of the cell. There are 11 chromosomes clearly visible at the 

 lower pole of the cell. 



16 Same as 15, except that the X-chromosome is seen. 



17 Equatorial plate view of dividing second spermatocj'te, showing the 

 presence of the Y-chromosome. 



18 Side view of second spermatocyte spindle, showing the precocious separa- 

 tion of the halves of the X-chromosome. 



19 Late anaphase of second maturation spindle, showing the presence of "the 

 X-chromosome. 



20 Same as above, except that the Y-chromosome is seen dividing. The 

 cells represented in figs. 19 and 20 are probably daughter cells of a single spermato- 

 cyte, as explained in text. 



44 



