280 MISCELLANEOUS OBJECTIONS TO THE [Chap. VIL 



in some new country. "We can, however, see in a general 

 manner that various causes might have interfered with 

 the development of a long neck or proboscis. To reach 

 the foliage at a considerable height (without climbing, 

 for which hoofed animals are singularly ill-constructed) 

 implies greatly increased bulk of body; and we know 

 that some areas support singularly few large quadrupeds, 

 for instance S. America, though it is so luxuriant; 

 whilst S. Africa abounds with them to an unparalleled 

 degree. Why this should be so, we do not know; nor 

 why the later tertiary periods should have been much 

 more favourable for their existence than the present 

 time. Whatever the causes may have been, we can see 

 that certain districts and times would have been much 

 more favourable than others for the development of so 

 large a quadruped as the giraffe. 



In order that an animal should acquire some struc- 

 ture specially and largely developed, it is almost indis- 

 pensable that several other parts should be modified and 

 co-adapted. Although every part of the body varies 

 slightly, it does not follow that the necessary parts 

 should always vary in the right direction and to the right 

 degree. With the different species of our domesticated 

 animals we know that the parts vary in a different man- 

 ner and degree; and that some species are much more 

 variable than others. Even if the fitting variations did 

 arise, it does not follow that natural selection would be 

 able to act on them, and produce a structure which ap- 

 parently would ■ be beneficial to the species. For in- 

 stance, if the number of individuals existing in a country 

 is determined chiefly through destruction by beasts of 

 prey, — by external or internal parasites, &c., — as seems 

 often to be the ease, then natural selection will be able 



