THE ALBINO SERIES OF ALLELOMORPHS IN 

 GUINEA-PIGS 



SEWALL WRIGHT 

 Bussey Institution 



Albinism is one of the most familiar color conditions 

 found in mammals. In all cases it has proved to be a 

 simple Mendelian recessive to the pigmented condition. 

 This was demonstrated for guinea-pigs by Castle and 

 Allen in 1903. In the present paper evidence will be pre- 

 sented showing that in guinea-pigs there are two grades 

 of pigmentation, intermediate between full intensity and 

 albinism, which form with these a series of four allelo- 

 morphs with dominance in the order of increasing pig- 

 mentation. 



The most highly pigmented condition is also the most 

 familiar. To this condition, which we may call intensity, 

 belong those types of guinea-pigs which show in the fur 

 intense black pigmentation or the intense orange-yellow 

 known as 1 'red," or both. Examples are the blacks, the 

 reds, the golden agoutis and the black-and-red tortoise- 

 shells of the fanciers. All of these have black eyes. 



The second condition in intensity and order of domi- 

 nance contains color varieties which have long been 

 known. In these black is reduced to a sepia-brown color 

 much like human brown hair, known very inappropriately 

 as 4 'blue." Red is reduced to yellow or cream. The 

 eye color remains black. Thus we have blues, creams, 

 silver agoutis and blue-and-cream tortoise-shells in place 

 of the four types mentioned as of the intense condition. 

 That these four so-called dilute types, as well as others 

 not mentioned, differ from the intense types by the same 

 factor or factors has long been known. It is shown by 

 the fact that one can start with any of these and by crosses 

 with the appropriate intense variety produce any other 

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