1 84 



REDUCTION OF THE CHROMOSOMES 



" ids," the latter being idcntiiied 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 



Fig. 92. — Reduction in the sperm.ifogenesis of Ascarh megalocephala, var. bivalens. [Brauer.] ^ 

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

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

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

 endw ise) . 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 centrosonie. 



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 Pig. 39 ; for the corresponding phenomena in 

 var. iiiiii'alens see Fig. 107. 



