192 DISTRIBUTION OF THE CHROMOSOMES 
Cc Cc’ 
Fig. 48.—Biston hirtaria; a, spermatogonial chromosomes; a’, primary 
spermatocyte chromosomes (reduced number). Biston zonaria; b, 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.) 
