304 LESSONS FKOM NATUKE. [CHAP. X. 



Yet, after all, Mr. Darwin concedes in principle the very 

 Marked cha- point in dispute, and yields all for which his oppo- 



racters cer- - 



tainiy arise nents need argue, when he allows that beautiful and 



indepen- 1 . . . 



dentiyofit. harmonious variations may occur spontaneously and 

 at once, as in the dark &quot;or spangled bars on the feathers of 

 Hamburg fowls ( Descent of Man, vol. i. p. 281). For what dif 

 ference is there, other than mere difference of degree, between 

 the spontaneous appearance of a few beautiful new feathers 

 with harmonious markings and the spontaneous appearance 

 of a whole beautiful clothing like that of the Tragopans ? 



Again, on Mr. Darwin s own showing, it is manifest that 

 male sexual characters, such as he would fain attribute to 

 sexual selection, may arise without any such action whatever. 

 Thus he tells us : &quot; There are breeds of the sheep and goat, 

 in which the horns of the male differ greatly in shape from 

 those of the female;&quot; and &quot;with tortoise-shell cats, the 

 females alone, as a general rule, are thus coloured, the males 

 being rusty-red&quot; (vol. i. p. 283). Now, if these cats were 

 only known in a wild state, Mr. Darwin would certainly bring 

 them forward amongst his other instances of alleged sexual 

 selection, though we now know the phenomenon is not due 

 to any such cause. A more striking instance, however, is 

 the following : &quot; With the pigeon, the sexes of the parent 

 species do not differ in any external character ; nevertheless, 

 in certain domesticated breeds the male is differently coloured 

 from the female. The wattle in the English carrier-pigeon, 

 and the crop in the pouter, are more highly developed in the 

 male than in the female ;&quot; and this has arisen, &quot; not from, but 

 rather in opposition to, the wishes of the breeders !&quot; This 

 amounts to a positive demonstration that sexual characters 

 may arise spontaneously, and, be it noted, in the class of 

 birds. 



As to intestinal worms, he says, on the authority of Dr. 

 Baird : 



&quot; The males of certain Entozoa differ slightly in colour from the 

 females ; but we have no reason to suppose that such differences have 

 been augmented through sexual selection.&quot; 



