140 DARWINISM chap. 



that they are inherited, and that they are constant. Ad- 

 mitting that this peculiar appendage is (as Mr. Eomanes says 

 rather confidently, " we happen to know it to be ") wholly 

 useless and meaningless, the fact would be rather an argument 

 against specific characters being also meaningless, because the 

 latter never have the characteristics which this particular 

 variation possesses. 



These useless or non-adaptive characters are, apparently, of 

 the same nature as the " sports " that arise in our domestic 

 productions, but which, as Mr. Darwin says, without the aid 

 of selection would soon disappear ; while some of them may 

 be correlations with other characters which are or have been 

 useful. Some of these correlations are very curious. Mr. 

 Tegetmeier informed Mr. Darwin that the young of white, yellow, 

 or dun-coloured pigeons are born almost naked, whereas other 

 coloured pigeons are born well clothed with down. Now, if 

 this difference occurred between wild species of different colours, 

 it might be said that the nakedness of the young could not be 

 of any use. But the colour with which it is correlated might, 

 as has been shown, be useful in many ways. The skin and its 

 various appendages, as horns, hoofs, hair, feathers, and teeth, 

 are homologous parts, and are subject to very strange correla- 

 tions of growth. In Paraguay, horses with curled hair occur, 

 and these always have hoofs exactly like those of a mule, while 

 the hair of the mane and tail is much shorter than usual. 

 Now, if any one of these characters were useful, the others 

 correlated with it might be themselves useless, but would still 

 be tolerably constant because dependent on a useful organ. 

 So the tusks and the bristles of the boar are correlated and 

 vary in development together, and the former only may be 

 useful, or both may be useful in unequal degrees. 



The difficulty as to how individual differences or sports can 

 become fixed and perpetuated, if altogether useless, is evaded 

 by those who hold that such characters are exceedingly common. 

 Mr. Romanes says that, upon his theory of physiological selec- 

 tion, "it is quite intelligible that when a varietal form is 

 differentiated from its parent form by the bar of sterility, any 

 little meaningless peculiarities of structure or of instinct should 

 at first be allowed to arise, and that they should then be allowed 

 to perpetuate themselves by heredity," until they are finally 



