NATURAL SELECTION 



comparatively short time the standard of our best racers might 

 be reached. But that standard has not for many years been 

 materially raised, although unlimited wealth and energy are 

 expended in the attempt. This is held to prove that there 

 are definite limits to variation in any special direction, and 

 that we have no reason to suppose that mere time, and the 

 selective process being carried on by natural law, could make 

 any material difference. But the writer does not perceive 

 that this argument fails to meet the real question, which is, 

 not whether indefinite and unlimited change in any or all 

 directions is possible, but whether such differences as do occur 

 in nature could have been produced by the accumulation of 

 variations by selection. In the matter of speed, a limit of a 

 definite kind as regards land animals does exist in nature. 

 All the swiftest animals deer, antelopes, hares, foxes, lions, 

 leopards, horses, zebras, and many others have reached very 

 nearly the same degree of speed. Although the swiftest of 

 each must have been for ages preserved, and the slowest must 

 have perished, we have no reason to believe there is any 

 advance of speed. The possible limit under existing con- 

 ditions, and perhaps under possible terrestrial conditions, has 

 been long ago reached. In cases, however, where this limit had 

 not been so nearly reached as in the horse, we have been 

 enabled to make a more marked advance and to produce a 

 greater difference of form. The wild dog is an animal that 

 hunts much in company, and trusts more to endurance than 

 to speed. Man has produced the greyhound, which differs 

 much more from the wolf or the dingo than the racer does 

 from the wild Arabian. Domestic dogs, again, have varied 

 more in size and in form than the whole family of Canidse in 

 a state of nature. No wild dog, fox, or wolf is either so 

 small as some of the smallest terriers and spaniels, or so large 

 as the largest varieties of hound or Newfoundland dog. And, 

 certainly, no two wild animals of the family differ so widely 

 in form and proportions as the Chinese pug and the Italian 

 greyhound, or the bulldog and the common greyhound. The 

 known range of variation is, therefore, more than enough for 

 the derivation of all the forms of dogs, wolves, and foxes 

 from a common ancestor. 



Again, it is objected that the pouter or the fan-tail pigeon 



