492 DE. ALFRED K. WALLACE ON 



species. Useful characters thus strictly limited are tlie necessary 

 and logical results of modification through survival of the fittest. 

 No agency has been shown to exist capable of producing useless 

 characters similarly limited. And as it is beyond the powers of 

 human reason to know absolutely that any characters so limited 

 as to be really specific are and always have been useless, it is 

 both unscientific and illogical co postulate such characters as 

 being present in all or many species, and therefore as consti- 

 tuting an essential characteristic feature of specific forms. 



The preceding discussion may, I hope, be considered sufficient 

 to show that useless specific characters, if they exist, can only 

 be the result of some comparatively rare and exceptional con- 

 ditions, and that they certainly are not, as has been alleged, a 

 general characteristic of species ; but it may be as well to notice 

 a few of the special cases which have been adduced by Mr. 

 E/Omanes and others as examples of their existence or as illus- 

 trating their formation. 



The Niata cattle of South America, which have strangely 

 upturned jaws, are said to breed very true and to form a definite 

 well-marked race which, if the character were not injurious but 

 simply iudifi'erent, might lead to the formation of a species 

 defined by this useless specific character. The short-legged 

 Ancon sheep, and the six-toed cats, are other examples of such 

 remarkable abnormalities or sports which have the curious 

 property of being strongly hereditary, and yet, apparently, of 

 never leading to the formation of new species. Almost all 

 students of evolution now admit that " sports " or large and 

 sudden divergencies from the specific type are not the materials 

 from which new species have been formed, the reason being that 

 they are extremely rare occurrences ; and when any such 

 " sport " appeared in a species, the individual presenting it would 

 either be avoided by its fellows and leave no off'spring, or by 

 repeated crossings with the normal type the sport would disappear. 

 "We may, no doubt, imagine conditions under which a sport of 

 this kind, once appearing in both sexes, might lead to the 

 formation of a breed and ultimately of a species ; but the 

 combination of conditions requisite to bring this about is so 

 improbable that we can only look upon it as a bare possibility. 

 But the question we are discussing is not whether, under certain 

 very rare and exceptional conditions, a few species may possibly 

 be formed which are distinguished only by altogether useless 

 characters, but whether such characters are common in the 



