94 



INHERITANCE IN GUINEA-PIGS. 



independent factors (p) . In the albino series, the dilution and red-eye 

 factors (C d and C r respectively) produce nearly if not quite identical 

 effects. In eye pigmentation, as in the black pigmentation of the fur, 

 first-order effects may be due either to different combinations in the 

 albino series or to other factors (p) ; but there is a sharp difference from 

 the effects on black fur, in that the dilution and red-eye factors produce 

 very different effects. In this case the intensity and dilution factors 

 apparently produce nearly identical effects. 



TABLE 41. 



2. Second-order effects in dilution of yellow, black, and probably 

 eye-color, are due to the unanalyzed residual heredity of different stocks. 

 In the stock at the Bussey Institution BW and South American blood 

 intensify as compared with dilute selection or 4-toe blood. This resid- 

 ual heredity seems to be more important in the case of black than 

 yellow, producing more overlapping of the ranges of the different albino 

 series combinations. 



3. In only one stock has the intensity of yellow at birth been observed 

 to change appreciably in the lifetime of the animal. In this case, the 

 dilute selection stock, the creams grow paler as they grow older. Sepia, 

 on the other hand, grows distinctly darker as the animals grow older hi 

 all stocks. In the imported South American stocks this darkening is 

 so pronounced that adults of any albino series combination, except 

 albinism itself (C a C a ), are practically black. 



INHERITANCE OF VARIATIONS IN THE AGOUTI PATTERN. 



Most wild rodents and many other mammals have a coat color of 

 the agouti type, viz, a predominantly black fur in which each hair 

 has a subterminal yellow band. In many cases, as in the mouse and 

 rat, the entire coat is fairly uniform in appearance. This is not true 

 in all cases, however. The color of Cavia cutleri has been described 

 at the beginning of this paper. It will be recalled that the color of the 

 belly is sharply distinct from that of the back, appearing wholly yellow 

 instead of ticked. Tame guinea-pigs of the agouti variety likewise 

 have this so-called light-bellied type of agouti. 



