GENETIC TYPE AND THE ENDOCRINES 33 



Darwin has made a further important statement concerning 

 the multiple origin of dogs : 



"From the resemblance of the half -domesticated dogs in 

 several countries to the wild species still living there, from 

 the facility with which they can often be crossed together, 

 from even half -tamed animals being so much valued by sav- 

 ages, and from the other circumstances . . . which favour 

 their domestication, it is highly probable that the domestic 

 dogs of the world are descended from the two well-defined 

 species of wolf, (viz. C. lupus and C. latrans), and from two 

 or three other doubtful species, (namely, the European, In- 

 dian, and North African wolves) ; from at least one or two 

 South American canine species ; from several races or species 

 of jackal; and perhaps from one or more extinct species." 

 (p. 26, v. 1.) 



Following this statement, Darwin characteristically points 

 out certain objections: 



"The belief that our dogs are descended from wolves, 

 jackals, South American Canidae, and other species, suggests 

 . . . important difficulty. These animals in their undomesti- 

 cated state, judging from a widely spread analogy, would 

 have been in some degree sterile if intercrossed; . . . these 

 animals keep distinct in the countries which they inhabit in 

 common. On the other hand, all domestic dogs, which are 

 here supposed to be descended from several distinct species, 

 are, as far as is known, mutually fertile together." (p. 31, v. 1.) 



"Notwithstanding the difficulties in regard to fertility, . . . 

 when w r e reflect on the inherent improbability 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 Canidae; when we reflect on the extreme an- 

 tiquity 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." (p. 34, v. 1.) 



"The intercrossing of the several aboriginal wild stocks, 

 and of the subsequently formed races, has probably increased 

 the total number of breeds, and . . . has greatly modified 

 some of them. But we cannot explain by crossing the origin 

 of such extreme forms as thoroughbred greyhounds, blood- 



