iv INTRODUCTION. 



Thus sometimes one and the same species may be greyish or reddish 

 or yellowish, or light, or dark ; and not only colour, but absolute size 

 may vary, individuals from Northern or Southern regions often differing 

 in this respect no less than in colour. 



The members of the family present also a very remarkable uniformity 

 in their internal structure as well as in their external conformation. If 

 we except the four species which form the three genera Cyon, Icticyon, 

 and Otocyon, an almost complete uniformity exists in the dentition, 

 although certain teeth may present differences in relative size and in 

 the details of their conformation. 



Dental characters are amongst the most constant which can be found 

 in the Canidcz \ nevertheless even these vary somewhat from individual 

 to individual, so that such minute characters, taken by themselves 

 absolutely, can rarely, if ever, afford a satisfactory basis for the distinction 

 and definition of a species. 



The general uniformity which exists in the external and internal con- 

 formation of all the species of the family is the more noteworthy, on 

 account of the exceedingly wide geographical distribution of the group ; 

 for some or other species of the Dog-family are to be found over the 

 greater part of the habitable globe, in addition to those which have been 

 disseminated by the civilized races of mankind. 



Although the existing Canidce differ so much from the other Carni- 

 vora which now inhabit the world, they show, as we shall see later, some 

 very curious resemblances to creatures of a very different kind 

 belonging to a most distinct order. These resemblances suggest various 

 questions as to the origin and affinities of the family : questions as to 

 which we have but little to say, but that little must be deferred to the 

 end of this introductory chapter. 



As already remarked, different naturalists have tried to divide the 

 CanidfB into a variety of genera, and they have also enumerated many 

 species distinguished by small differences of colour or size. Till within 

 the last thirty years very little attention was paid to variation, and 

 there was a general disposition to accept any single exceptionally 

 coloured skin as sufficient evidence of the existence of a new and distinct 

 species. Until a considerable number of skins and skulls of one and 



