1 84 



REDUCTION OF THE CHROMOSOMES 



"ids," the latter being identified with the visible chromomeres or 

 chromatin-granules. The ids finally are associated in linear groups 

 to form the "idants" or chromosomes. Since the biophores differ 

 qualitatively, it follows that the same must be true of the higher units 



G 



D 



FJ 



\ 





It 



K 



Fig. 92. Reduction in the spermatogenesis of Ascarls megalocephala, var. bivaletis. [BRAi ; KR.] " 

 A-G. Successive stages in the division of the primary spermatocyte. The original reticulum 

 undergoes a very early division of the chromatin-granules which then form a doubly split spireme- 

 thread, B. This shortens (C), and breaks in two to form the two tetrads (D in profile, E viewed 

 endwise). F. G. H. First division to form two secondary spermatocytes, each receiving two dyads. 

 /. Secondary spermatocyte. J. K. The same dividing. L. Two resulting spermatids, each with 

 two single chromosomes and a centrosome. 



formed by their aggregation. Hence each chromosome has a dis- 

 tinct and definite character of its own, representing a particular group 

 of hereditary qualities. From this it follows that the number of 



1 For division of the spermatogonia see Fig. 39 ; for the corresponding phenomena in 

 var. unii'dlens see Fig. 107. 



