DISTRIBUTION OF THE CHROMOSOMES 145 



f 



*** 



* - * 



a a' 



'*/* 



FIG. 48. Biston hirtaria; a, spermatogonial chromosomes; a', primary 

 spermatocyte chromosomes (reduced number). Biston zonaria; 6, sper- 

 matogonial chromosomes; b', primary spermatocytes (reduced number). 

 Hybrid, out of zonaria female by hirtaria male; c, spermatogonial chro- 

 mosomes; c', primary spermatocytes. (After Harrison and Doncaster.) 



