Page:The Zoologist, 4th series, vol 2 (1898).djvu/424

392 of British Guiana, states that "the purple tints on the throat, breast, and body of Cotinga cayana, C. cærulea, and Xipholena pompadora can be changed to a brilliant red by exposing them to heat in such a way as to affect those feathers without singeing — an indication of the possibilities in nature under changing thermal conditions." Where everything is of one assimilative hue, such universal protection—if it were such—would rather tend to neutralization in all such properties, and other qualities would be necessary in the struggle for existence, the absence of which might mean starvation and extermination to many species, or vice versâ—the correlative undue multiplication of others; facts which certainly do not appear on the surface. An American writer in studying the same problem has given a similar opinion. As he observes, "its tendency is to bring the colours of the animals to agree with those of its surroundings; for this reason it has been classed as protective colouration, notwithstanding the fact of its occurrence on all the species of a locality whether in need of protection or not." The very essence of the theory of protective resemblance, as a means of survival consequent upon the slow but sure action of natural selection, is a special, not a general effect,—a particular, not an universal attribute,—but one of the many and diverse qualifications which enable animals and plants to survive in the competitive struggle for existence. If such a suggestion is reasonable or probable, we ought at least to find some supportive facts, and these can be gathered, though scantily, for the observations of travellers and naturalists do not appear to have been greatly attracted in that quarter. M.