86 INHERITANCE IN GUINEA-PIGS. 



This dull black can not be due to an allelomorph of albinism between 

 intensity (C) and dilution (C d ), since it is a condition which can be 

 transmitted by albinos. Indeed, the albinos themselves of the BW 

 and 4-toe stocks differ conspicuously in appearance. The BW albinos 

 have jet black ears and feet, dark smudges on- the nose, and usually 

 some sootiness on the back. The 4-toe and most other albinos (at the 

 Bussey Institution) have very much less black on ears, nose, and feet, 

 and the rest of the fur is pure white. 



There are parallel variations hi the intensity of red in these stocks. 

 The occasional red spots in the BW race are of a very intense red 

 (standard redo). In the 4-toe and other dull stocks the red is consider- 

 ably less intense, especially at the base of the hair. The most dilute 

 grade found hi tame guinea-pigs known to have factor C is yellow 2 

 (D12 cross 35-1). 



The wild Cavia cutleri is quite light in color. The black of the fur 

 is a dull slaty color, more like the dull black of the 4-toes than any other 

 color in tame guinea-pigs. The yellow on the back is about yellow 3 , 

 on the belly creams. In spite of the resemblance to tame yellow 

 agoutis, Cavia cutleri has the intensity and not the dilution factor. 

 When crossed with animals of the BW race, whether blacks or albinos, 

 the young are intermediate in intensity and would be called intense 

 (Parti). Crossed with black animals of the 4-toe race, the young 

 are but little more intense than Cavia cutleri. (See plate 3.) 



Summing up : All variations maybe found among intense guinea-pigs, 

 from uniform black to a dull slaty black 2 and from red to yellow 2 . In 

 the dull grades the hair is especially dull at the base. These variations 

 are hereditary, but have not been analyzed. The hereditary factors 

 for these variations in intense guinea-pigs are responsible for visible 

 differences among albinos. It is to be expected, as indeed is the case, 

 that variations will be found among dilutes, for which these same 

 unanalyzed hereditary differences of different stocks are responsible. 

 Finally, the residual heredity of all tame guinea-pigs has more intensi- 

 fying effect than that of Cavia cutleri, the wild species. 



MULTIPLE ALLELOMORPHS. 



The presence of at least four allelomorphs in the albino series suggests 

 the hypothesis that other allelomorphs in the series may be responsible 

 for the intermediate grades hi intensity. It is a tempting hypothesis 

 to suppose that the continuous series of variations is correlated with a 

 continuous series of allelomorphs, such that each grade of intensity is 

 dominant over all lower grades. If this were the case a stock of 

 dilutes, hi which all derive their dilution from a single gamete of one 

 animal, should be fairly constant hi their degree of dilution. Again, the 

 cross of dilute by dilute should never give young more intense than the 

 darker parent. 



