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THE AMERICAN NATURALIST [Vol. L 



such matings. Those offspring grouped around the upper mode 

 were spotted, and had a formula PpSs. When mated inter se or 

 back to recessive spotted, they gave, besides spotted and selfs, 

 black-eyed whites; apparently because the combination Ppss 

 could again be formed. The dominant spotting factor, P, evi- 

 dently acts more vigorously upon recessive spotting than upon 

 self. It can not restrict the more extended pigmentation of a 

 self coat completely. Hence, half of the F x individuals (those 

 with the formula PpSs) were spotted, or, to describe them more 

 accurately, spotted with frequent and varying amounts of silver- 

 ing. The dominant spotting factor, P, can, however, restrict the 

 limited pigmentation of a recessive spotted coat completely or 

 almost completely. Hence animals with the formula Ppss were 

 black-eyed whites. 



The origin of our new pink-eyed white forms, which resemble 

 albinos so closely as to be indistinguishable from them, is evi- 

 dently due to the substitution of the pink-eye factor for dark- 

 eye in black-eyed whites, and not due to the loss of the color 

 factor C. In our cultures, the black-eyed whites have the for- 

 mula PpssDDCC and the corresponding pink-eyed whites had 

 the formula PpssddCC where D and d represent dark eye and 

 pink eye respectively, and C represents the color factor. We 

 have also produced black-eyed white forms heterozygous in dark 

 eye, PpssDd. Black and brown are likewise interchangeable in 

 the dark-eyed whites, for black-eyed whites, heterozygous in 

 black, have been produced. I see no reason why brown-eyed 

 whites can not be produced in the usual Mendelian fashion by 

 mating black-eyed whites to browns, and recovering the white 

 pelage with brown eyes in the F 2 generation. Mating the spotted 

 F x offspring inter se should give, among others, individuals with 

 the formula PpssbbCC. These would be brown-eyed whites,— 

 white because of the combined action of P and s, and brown 

 simply because they lack the differential factor B which changes 

 brown into black. 



The occurrence of pink-eyed whites which resemble albinos may 

 have some bearing on an anomalous case cited by Bateson ( '04) 

 as follows : "the production of colored animals by albinos, is not, 

 so far as I know, illustrated by a single case, with the following 

 exception. In the later editions of < < Fancy Mice ' ' (Upcott Gill) , 

 Dr. Carter Blake, formerly secretary of the Anthropological In- 

 stitute commenting on the statement that albino mice of whatever 



