340 THE DESCENT OP MAN. 



"brilliancy of their colors" serves as "a better mark for king- 

 "fishers, terns, and other birds which are destined to keep the 

 "number of these fishes in check;" but at the present day few 

 naturalists will admit that any animal has been made conspicuous 

 as an aid to its own destruction. It is possible that certain fishes 

 may have been rendered conspicuous in order to warn birds and 

 beasts of prey that they were unpalatable, as explained when 

 treating of caterpillars; but it is not, I believe, known that any 

 fish, at least any fresh-water fish, is rejected from being distaste- 

 ful to fish-devouring animals. On the whole, the most probable 

 view In regard to the fishes, of which both sexes are brilliantly 

 colored. Is that their colors were acquired by the males as a 

 sexual ornament, and were transferred equally, or nearly so, to 

 the other sex. 



We have now to consider whether, when the male differs in a 

 marked manner from the female in color or in other ornaments, 

 he alone has been modified, the variations being inherited by his 

 male offspring alone; or whether the female has been specially 

 modified and rendered Inconspicuous for the sake of protection, 

 such modifications being inherited only by the females. It is 

 impossible to doubt that color has been gained by many fishes 

 as a protection: no one can examine the speckled upper surface 

 of a fiounder, and overlook its resemblance to the sandy bed of 

 the sea on which It lives. Certain fishes, moreover, can through 

 the action of the nervous system, change their colors in adapta- 

 tion to surrounding objects, and that within a short time.''^ One 

 of the most striking instances ever recorded of an animal being 

 protected by Its color (as far as it can be judged of in preserved 

 specimens), as well as by its form, is that given by Dr. Gunther" 

 of a pipe-fish, which, with its reddish streaming fllarnents, is 

 hardly distinguishable from the sea- weed to which It clings with 

 its prehensile tail. But the question now under consideration is 

 whether the females alone have been modified for this object. 

 We can see that one sex will not be modified through natural se- 

 lection for the sake of protection more than the other, supposing 

 both to vary, unless one sex is exposed for a longer period to 

 danger, or has less power of escaping from such danger than the 

 other; and it does not appear that with fishes the sexes differ in 

 these respects. As far as there is any difference, the males, from 

 being generally smaller and from wandering more about, are 

 exposed to greater danger than the females; and yet, when the 

 sexes differ, the males are almost always the more conspicuously 

 colored. The ova are fertilized immediately after being deposited; 

 and when this process lasts for several days, as in the case of 



"' G. Pouohet, L'Institut, Nov. 1, 1871, p. 134. 

 == 'Proc. Zoolog-. Soc' 1865, p. 327, pi. xlv. and xv. 



