NATURAL SELECTION CRITICISED. 295 



even among insects and birds the greater number are plainly 

 coloured, and show no great difference of sex in numerous marine 

 creatures, whose mode of life renders concealment unnecessary, 

 ' warning colours ' are futile, and sexual coloration impossible, 

 the frequently brilliant colours are entirely due to pigment de- 

 posited in the skin. On the other hand, in butterflies and birds, 

 where sexual selection and so forth is conceivable, the colours are 

 largely produced by mechanical causes affecting the structure of 

 feathers or scales the varying coloration of the common earth- 

 worm is due to different pigments, but the earthworm being blind 

 as well as hermaphrodite, can have no leaning towards a male of a 

 specially bright hue the rook as he follows the plough is no 

 respecter of anneloids' persons, and gobbles up all that comes in 

 his way, brown and green, purple and red. It is not too much to 

 say that nearly all, if not quite all, birds in which the two sexes 

 (as in the peacock) show a marked disparity of coloration, owe their 

 brilliant hues to structural peculiarities of the feathers, and not to 

 pigments. But if this be so, how is it that we get so great a variety 

 of tints among animals which are exclusively coloured by the 

 pigments ? The only answer to this question at present seems to 

 be to say that there is no answer. The bile shows differences of 

 colour in various animals, being green in one and yellow in another ; 

 the inside of one lizard's body is coloured deep-brown, of another 

 it is not coloured at all ; birds' eggs show the most varied hues, which, 

 except in a very few cases, can be of no use whatever, as they are 

 hidden by the sitting hen." 



Instead of quoting many marked passages, I will 

 just observe of so familiar a book as the Natural History 

 of Selborne, that if any one will read it in this connection, 

 he may be apt to find himself not by any means firm 

 as a possible Darwinian in conclusion. So many things 

 are double-sided. Thus, if we accentuated the differences 

 that appear in the stock of horses which is said to split 

 up into race-horses, etc., we only forget the fact that 

 they are all horses still. In the same way, it is no 

 doubt true that the foot of the tame duck becomes 

 heavier, as its wing, possibly, lighter ; and it may be all 

 very well for Mr. Darwin to think of this in his own 

 direction. Nevertheless, wild or tame, they are not the 



