34 DOGS. Chap. I. 



exhibit lier proper periods ; but this case was certainly 

 exceptional, as numerous instances have occurred of fertile 

 hybrids from these two animals. In almost all experiments 

 on the crossing of animals there are so many causes of doubt, 

 that it is extremely difficult to come to any positive con- 

 clusion. It would, however, appear, that those who believe 

 that our dogs are descended from several species will have 

 not only to admit that their offspring after a long course of 

 domestication generally lose all tendency to sterility when 

 crossed together ; but that between certain breeds of dogs and 

 some of their supposed aboriginal parents a certain degree of 

 stei-ility has been retaiued or possibly even acquired. 



Notwithstanding the difficulties in regard to fertility 

 given in the last two paragraphs, when we reflect on the 

 inherent improbabilit}' of man having domesticated through- 

 out the world one single species alone of so widely distribiited, 

 so easily tamed, and so useful a group as the Canidee ; when 

 we reflect on the extreme antiquity of the different breeds ; 

 and especially when we reflect on the close similarity, both 

 in external structure and habits, between the domestic dogs 

 of various countries and the wild species still inhabiting 

 these same countries, the balance of evidence is strongly in 

 favour of the multiple origin of our dogs. 



Differences between the sevet-al Breeds of the Dog. — If the 

 several breeds have descended from several wild stocks, their 

 difference can obviously in part be explained by that of their 

 jiarent species. For instance, the form of the greyhound 

 may be partly accounted for by descent from some such 

 animal as the slim Abyssinian Canis simensis,^'^ with its 

 elongated muzzle j that of the larger dogs from the larger 

 wolves, and the smaller and slighter dogs from the jackals : 

 and thus perhaps we may account for certain constitutional 

 and climatal differences. But it would be a great error 

 to suppose that there has not been in addition ^^ a large 



^- Riippel, ' Neue Wirbelthiere von Museum. 

 Abvssinien,' 1835-40 ; ' Mammif.,' s. " Even Pallas admits this ; see 



39," pi. xiv. There Ls a specimen 'Act. Acad. St. Petersburgh,' 1780, 



of this fine animal in the British p. 93. 



