ANIMAL COLOURING 
223 
of scientific insight. The facts of resemblance them- 
selves are so wonderful, and the contrast between the 
colours of the sexes in birds so startling, that the 
temptation to make a great principle like that of 
natural selection fit the exact requirements of each 
case, and to explain the complexity of Nature in a 
sentence, is almost irresistible. It is quite possible 
that the principle of natural selection, which gives a 
perfect explanation of the wonderful phenomena of 
“ protective mimicry,” may also be the master-key to 
the remaining problems of animal hues. The chief 
difficulties which remain, after accounting for pro- 
tective coloration, are, first, the extraordinary differ- 
ences between the tints and plumage of male and 
female in many birds; and, secondly, the conspicuous 
colours of certain creatures by which the attention of 
their enemies must necessarily be attracted. The first 
of these obvious difficulties has been explained by 
what is called “ sexual selection,” which is an auxiliary 
to the general law of natural selection. The female 
pheasants, or birds of paradise, or pigeons, as the case 
may be, by an enduring good taste in choosing for 
their mates those with the brightest plumage and 
finest wattles and spurs, have played their part in the 
general scheme of evolution so well, that their progeny 
have in time developed all the beauties which they 
now possess. That theory is obviously quite con- 
sistent with the general law. It accounts logically in 
part, if not entirely, for the perilous beauties of the 
stronger sex. But there are creatures in gorgeous 
