20 The Descent of Man 



elusion that sexual selection is the one universal cause of 

 sexual characters, when similar effects to those which it is 

 supposed to cause take place in its absence. 



But, indeed, what are the data on which Mr. Darwin 

 relies as regards birds ? As before said, they are ' display ' 

 by the males, the 'greater brilliancy and ornamentation of 

 these,' and the ' occasional preference ' by females in confine- 

 ment for particular males. Is there here any sufficient 

 foundation for such a superstructure ? In the first place, 

 in insects, e.g. butterflies, we have often many brilliant males 

 crowding in pursuit of a single female. Yet, as Mr. Wallace 

 justly observes, ' Surely the male who finally obtains the 

 female will be either the most vigorous, or the strongest- 

 Avinged, or the most patient — the one who tires out or beats 

 off the rest.' Similarly in birds strength and perseverance 

 will, no doubt, generally reward the suitor possessing those 

 qualities. Doubtless, also, this will generally be the most 

 beautiful or most melodious ; but this will simply be because 

 extra beauty of plumage or of song, will accompany super- 

 eminent vigour of constitution and fulness of vitality. What 

 has been before said as to the fierce combats of cock-birds 

 must be borne in mind. 



But that internal spontaneous powers are sufiicient to 

 produce all the most varied or bizarre sexual characters 

 which any birds exhibit, is actually demonstrated by the 

 class of insects, especially caterpillars, which from their sex- 

 less, undeveloped state can have nothing to do with the kind 

 of selection Mr. Darwin advocates. Yet amongst caterpillars 

 we not only find some ornamented with spots, bands, stripes, 

 and curious patterns, ' perfectly definite in character and of 

 the most briUiantly contrasted hues. We have also many 

 ornamental appendages ; beautiful fleshy tubercles or tent- 

 acles, hard spines, beautifully coloured hairs arranged in 

 tufts, brushes, starry clusters, or long pencils, and horns on 



