60 THE MENDEL JOURNAL 



phase between white and black in nigrescent individ- 

 uals or partial melanos. True melanos are wholly- 

 black, just as pure albinos are wholly white ; but 

 partial melanos are quite common, black-and-tan 

 dogs being a familiar instance. If a black-and-tan 

 dog be compared with a pale-coloured wolf, it is 

 obvious that the tan round the mouth, over the eyes, 

 on the paws, and other parts of the dog correspond 

 exactly with light areas on the wolf, and that the 

 black parts of the dog correspond in the same way 

 with the greyish-black pigmented parts of the wolf.* 

 Just as black-and-tan dogs are partial melanos, so 

 are black leopards, as a rule, if not always, partial 

 melanos ; that is to say, they are seldom if ever 

 uniformly black. The intermediate spaces are a 

 little paler than the spots ; and the underside of the 

 body, which in the normal animal has a pure white 

 ground colour, is very dark tan. Black domestic 

 Cats, on the contrary, are generally complete 

 melanos when adult, the pattern being invisible 

 because the hair is everywhere as black as the pattern. "f 

 Black and white are thus two extremes of 

 colour mutation, yellowish-red or tan being the 

 intermediate phase. These three phases are usually 

 called melanistic, albinistic, and erythristic. All 

 three are common in domestic Cats. The majority 

 of Cats seen roaming at large and practically uncared 



* R. I. Pocock, Annals Magazine Natural History (7), xix., pp. 

 192-194. 



t Black cats commonly have a white speck on the chest at the 

 anterior end of the sternum. This white speck is frequently present 

 in Scotch wild cats. The persistence of the whiteness of this spot 

 in black cats is a puzzling fact. 



