142 THE AMEBIC AN NATURALIST [Vol.XLIX 



ally the most highly pigmented regions in the dilute and 

 red-eye conditions. In the albinos, yellow disappears en- 

 tirely, just as in the red-eyes. The eyes are pink, due 

 to the loss of all pigment from the iris and retina. The 

 blacks and golden agoutis are replaced by sooty albinos ; 

 the reds, by clear albinos ; and the black-and-red tortoise- 

 shells, by albinos in which nose, feet and ears are sooty 

 or white, depending on the location of the spots. 



The effects of the four allelomorphs on the appearance 

 of eye and fur may be tabulated as follows : 



Intensity ! Black 



Dilution ! Black 

 Red-eye Red 

 Albinism Pink 



It should be added that dilution of pigmentation may be 

 produced by other factors than members of the albino 

 series of allelomorphs. In the foregoing discussion such 

 factors have been assumed to be absent. It may be said, 

 however, that by starting with variations which owe their 

 dilutions to factors which are independent of the albino 

 series, doubly dilute varieties have been produced on in- 

 troducing the dilution or red-eye allelomorphs of albi- 

 nism. The effects of dilution, red-eye and albinism on 

 brown pigment are parallel in all cases to their effects on 

 black. 



It should be said that the sepia (or "blue") due to the 

 dilution factor, or to the red-eye factor, varies through a 

 wide range which intergrades with black. Thus Castle 

 (1905) and Sollas (1909) recognized that both intense and 

 dilute forms of pigmentation occur commonly in guinea- 

 pigs, but did not suggest any factorial explanation be- 

 cause of this intergrading. The inheritance of these fluc- 

 tuations is at present under investigation. 



If intensity, dilution, red-eye and albinism are allelo- 

 morphs, gametes should always carry one, but only one, 

 of the four. Zygotes must always have two representa- 



