172 



THE AMERICAN NATURALIST 



[Vol. LIV 



colored individuals of classes (3) and (4) and no sterility above 

 the ordinary would be expected. 



It is also interesting to note that theoretically the colored 

 females of class (4) would when crossed with ordinary white 

 males yield colored females of the normal type. Thus: 



It may be objected that changes from a hypostatic factor to 

 its epistatic allelomorph are not frequent. This is admitted. On 

 the other hand, they have been several times reported by investi- 

 gators, among others by Morgan, in Drosnf/hiln, and by the writer, 

 in mice. In this connection it is interesting to note that the white 

 doves referred to are not totally unpigmented being merely 

 dilute, a fact easily observed in their eye color and found by 

 Strong (1912) to hold true for their plumage. 



2. In Canaries.— The factors involved are the allelomorphie P 

 for dark eye color and p for pink-eye color. The quantitative 

 relation between the two is somewhat similar to that described in 

 doves though considerably less marked. The factorial change 

 appears to be extremely rare and to be from the p to the P condi- 

 tion. The following results would be expected if the change 

 occurred in the pink-eyed male. 



(4) PpFFMm = dark-eyed Um*\e*r * ' 



Here as in doves the homozygous and heterozygous dark-eyed 

 males would be distinguishable only after a carefully controlled 

 breeding test. The dark-eyed females would be the only excep- 

 tional phenotypically distinct color class expected. 



If the change occurred in the dark-eyed female instead of in 

 the pink-eyed male we should have the following condition. 



