Explanation of Plate IX. 



Fig. 34. Photomicrograph of early spireme stage of first spermatocyte, show- 

 ing peripheral position of the accessory chromosome x. At the left, secondary 

 spermatogonia, last generation. >< 1300. 



Fig. 35. A late prophase, showing accessory chromosome x, and spindle re- 

 mains s (cf. figs. 3 and 4). >< 1300. 



Fig. 36. Coarse spireme of first spermatocyte. X 1300. 



Fig. 37. Prophase, with chromosomes in the form of long segments. At a, 

 the cell drawn in figure 9. In the cyst at the left are spermatocytes in a later 

 stage, with the chromosomes homogeneous. X1000. 



Fig. 38. Prophase with segments divided longitudinally and across. At a is 

 is one shown en face. Accessory chromosome at x. XlOOO. 



Fig. 39. Metaphase and anaphase of first spermatocyte. The accessory chro- 

 mosome x at one pole of the spindle. Lagging chromosome at c. X1300. 



