34 DISTINCTION BETWEEN SPECIES AND VARIETIES. 



of adapting themselves to changes in the circumstances of their 

 residence, mode of life, &c,, that their utility to Man arises. 

 There is none which shows this more strongly than the Dog, 

 which is the companion of Man in every part of the globe, and 

 which presents more striking varieties of form than any other 

 species. Not only do the different races of Dogs vary in the colour 

 and quantity of their hair, but also in the proportions of the dif- 

 ferent parts of their body (which is show r n as much in their skele- 

 tons as in the living animals), and even in their instincts, which 

 in most animals are invariable. Look, for example, at the Grey- 



Fiu. 2. CUBAN MASTIFF. 



hound (Fig. 1) and the Mastiff (Fig. 2), the Bloodhound (Fig. 

 3) and the Spaniel (Fig. 4) ! We should scarcely imagine that 

 any period of time, any external influences, could convert one 

 into the other. Yet the Zoologist has no hesitation in affirming 

 that they had a common origin ; since it is found that their dis- 

 tinct forms are preserved, only so long as they are matched in 

 breeding with forms of the same kind. For if the different races 

 of Dogs are allowed to breed promiscuously together, and escape 

 from the influence of Man, returning to their original savage mode 

 of life, the varieties gradually disappear, and the races all blend 

 together, after a few generations, into one common type, which 



