GENES AND CHARACTERS 



315 



out this conclusion. Under such conditions it is apparent that 



only two of the characters can be represented in any one individual. 



The characters that have given such a wealth of material to 



the geneticist in Drosophila are mutations. There is no reason 



Fig. 181. — Diapram of the reciprocal cross of Fip;. ISO, i. e., white-eyod female 

 and red-eyed male of D. melunogcidcr. W indicates red and w white. (From 

 Morgan et al., Mechanism of Mendelian Heredity, with the permission of 

 Henry Holt and Company.) 



