8 COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



BLACK. 



In the black variety, black pigment predominates over the other two 

 sorts and obscures them. But I have never been able to obtain it in 

 a pure state. Chocolate is invariably associated with it, and usually 

 hairs can be found somewhere on the body which show the presence 

 of the red-yellow pigment also. 



In the ordinary black hair chocolate pigment predominates in the 

 cortex, black in the medulla. I am unable to say whether the red- 

 yellow pigment is present with them or not, but I am inclined to think 

 that in some cases at least it is, for here and there on the body one can 

 frequently find a hair devoid of the black and chocolate pigments, and 

 such a hair commonly shows a red or yellow pigmentation. Still there 

 are reasons for supposing that with proper attention a black variety 

 could be produced which would have no red or yellow in its coat, just 

 as red or yellow animals are obtained free from black and chocolate. 



The black, like the red-yellow variety, occurs in forms more or 

 less heavily pigmented, the lighter shades being known as blue. The 

 latter can be produced by crossing black animals with red or yellow 

 ones, or with albinos of certain sorts. Blue animals bear the same 

 relation to black ones as silver agoutis to golden agoutis. Blue and 

 silver agouti are dilute forms of black and golden agouti, respectively. 

 In a blue animal the black and chocolate pigments are less abundant, 

 and the red-yellow pigment, if it appears on separate hairs, is of a light 

 (yellow) shade. 



ALBINO. 



_ 



The albino or white variety, though apparently the simplest as re- 

 gards pigment characters, is in reality the most complex. Albinos 

 have pink eyes, the color of which is due not to a pigment, but to the 

 blood seen through the transparent eye. The hair is likewise unpig- 

 mented at birth, and may remain of this character throughout life 

 over the greater part of the body. Albino mice and ordinary albino 

 rabbits apparently never develop pigment in any part of their coat, but 

 such is not the case in cavies. Though I have carefully sought them, 

 I have never yet Keen albino individuals which in adult life did not 

 form pigment in some region or other of their coat. This pigment 

 makes its appearance first and chiefly at the extremities of the body 

 on the ears, the feet, and the nose but may in extreme cases extend to 

 the hairs of the body coat also. To the unaided eye the hairs of the 

 extremities are of a sooty black color ; the microscope shows them to 

 contain chocolate pigment, with an occasional granule of black. 



In the body hairs I have in one case identified reddish-yellow granules 

 without those of other sorts. Thev are not at all abundant and are 



j 



found principally at the tip of the hair, so that the coat looks like an 



