SEXUAL SELECTION 345 



Many of fhe lower animals, wlietlier hermaplirodites or 

 with separate sexes, are ornamented witt tlie most brilliant 

 tints, or are shaded and striped in an elegant manner; for 

 instance, many corals and sea-anemones (Actinise), some 

 jelly-fish (Medusae, Porpita, etc.), some Planarise, many 

 star-fishes. Echini, Ascidians, etc. ; but we may conclude 

 from the reasons already indicated, namely, the union of 

 the two sexes in some of these animals, the permanently 

 af&xed condition of others, and the low mental powers of 

 all, that such colors do not serve as a sexual attraction, and 

 have not been acquired through sexual selection. It should 

 be borne in mind that in no case have we sufficient evidence 

 that colors have been thus acquired, except where one sex 

 is much more brilliantly or conspicuously colored than the 

 other, and where ther-e is no difference in habits between 

 the sexes sufficient to account for their different colors. 

 But the evidence is rendered as complete as it can ever be, 

 only when the more ornamented individuals, almost always 

 the males, voluntarily display their attractions before the 

 other sex; for we cannot believe that such display is use- 

 less, and if it be advantageous, sexual selection will almost 

 inevitably follow. "We may, however, extend this conclu- 

 sion to both sexes, when colored alike, if their colors are 

 plainly analogous to those of one sex alone in certain other 

 species of the same group. 



How, then, are we to account for the beautiful or even 

 gorgeous colors of many animals in the lowest classes? 

 It appears doubtful whether such colors often serve as 

 a protection; but that we may easily err on this head will 

 be admitted by every one who reads Mr. "Wallace's excellent 

 essay on this subject. It would not, for instance, at first 

 occur to any one that the transparency of the Medusae, or 

 jelly-fishes, is of the highest service to them as a protection ; 

 but when we are reminded by Hackel that not only the 

 medusae, but many floating mollusca, crustaceans, and even 

 small oceanic fishes partake of this same glass-like appear- 

 ance, often accompanied by prismatic colors, we can hardly 



