Chap. I. DIFFERENCES OF BREEDS. 33 



her keeper, she did not fully exhibit her proper periods ; but this 

 case, from the numerous instances of fertile hybrids from these 

 two animals, was certainly exceptional. In almost all experi- 

 ments 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 sup- 

 posed aboriginal parents a certain degree of sterility has been 

 retained or possibly even acquired. 



Notwithstanding the difficulties in regard to fertility given in 

 the last two paragraphs, when we reflect on the inherent im- 

 probability of man having domesticated throughout the world 

 one single species alone of so widely distributed, so easily 

 tamed, and so useful a group as the Canidse ; 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 several Breeds of the Bog. — If the 

 several breeds have descended from several wild stocks, their 

 difference can obviously in part be explained by that of their 

 parent-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, 51 with its elongated muzzle ; 

 that of the larger dogs from the larger wolves, and the smaller 

 and slighter dogs from 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 52 a large amount of variation. The intercrossing of the 

 several aboriginal wild stocks, and of the subsequently formed 



« Riippel < Neue Wirbelthiere von animal in the British Museum. 



Abyssmien 1835-40 ; Mammif.,' s. 39, * 2 Even Pallas admits this ; see ' Act. 



pi. xiv. There is a specimen of this fine Acad. St. Petersburgh/ 1780, p 93. 



VOL. I. 



