102 Mr. R. I. Pocock on the 



broaiUy roniidcil, half tho widtli of the apex, which is slightly 

 roniitled iiiwaidl}-; the bordorinpj keel is shininp^, flat, 

 smooth, broad at the base ; the ajiox i>? broadly depressed, 

 finely rugosely punctured, the rest iiregidaily ])unctured and 

 aciculatcd. 



XXII, — On the Blach-and-tnn Pattern of Domestic Doga 

 (Canis faniiliaris). By 11. I. Pocock", F.L.S., F.Z.S., 

 Superintendent of the Zoological Society's Gardens. 



1\ 'The Variation of Animals and Plants under Domestication,' 

 |i[). 33-3.") (ed. 1905), the black-and-tan pattern of domestic 

 dogs is discussed at some length. Darwin was led to investi- 

 gate the question somewliat fully in tiie hope that lie might 

 thereby discover a clue to the origin of our breeds amongst 

 wild species; but failing to find the tan-coloured spots over 

 the eyes either depicted in any drawings of wolves, j ickals, 

 and other species of Canis, or visible on any skins in the 

 collection of the British Museum, he came to the conclusion 

 that the coexistence of these spots with tan-coloured paws is 

 probably a case of correlated variation. 



Aj)art from suggesting that a now extinct species involved 

 in the pedigree of domestic dogs may have j)ossessed these 

 spots, he offered no other explanation of the " highly remark- 

 able" fact of the occurrence of these spots in " exti-emely 

 different breeds, living in various parts of the world." 



The phenomenon, however, appears to me to be susceptible 

 of a quite simple exj)lanation. 



In a typical black-and-tan dog, whatever the breed, the 

 tan is distributed as follows : — on the sides of the muzzle and 

 H|j3, the lower half of the cheeks, and the throat; a spot 

 over the inner corner of the eye, very frequently on the inside 

 of the ear, and as a large patch on each side of the chest above 

 the base of the fore legs; on the paws of the fore legs and on 

 the hind legs Ijelow the hock ; to a somewhat variable degree 

 on the inner sides of the legs, but extending over the front of 

 the hind leg up to the body ; on the circumanal area and on 

 the underside of the tail, at least in its proximal portion. The 

 lest of the animal is black. If a dog thus coloured be com- 

 pared with many of the common wild species of Canidae, it 

 will be seen that the tan occurs over areas which in the wild 

 species are paler than the rest of the body, owing to the 

 fading or ab-encc of the black annuli which prevail in the 



