in PROTECTIVE RESEMBLANCES AMONG ANIMALS 35 



which it brought to light and made use of. The series of 

 Natural History volumes in Lardner's Cabinet Cyclopcedia, in 

 which Mr. Swainson developed it in most departments of the 

 animal kingdom, made it widely known ; and in fact for a 

 long time these were the best and almost the only popular 

 text-books for the rising generation of naturalists. It was 

 favourably received too by the older school, which was per- 

 haps rather an indication of its unsoundness. A considerable 

 number of well-known naturalists either spoke approvingly of 

 it, or advocated similar principles, and for a good many years 

 it was decidedly in the ascendant. With such a favourable 

 introduction, and with such talented exponents, it must have 

 become established if it had had any germ of truth in it ; 

 yet it quite died out in a few short years ; its very existence 

 is now a matter of history ; and so rapid was its fall that 

 its talented creator, Swainson, perhaps lived to be the last 

 man who believed in it. 



Such is the course of a false theory. That of a true one 

 is very different, as may be well seen by the progress of 

 opinion on the subject of Natural Selection. In less than 

 eight years The Origin of Species has produced conviction 

 in the minds of a majority of the most eminent living men 

 of science. New facts, new problems, new difficulties as they 

 arise are accepted, solved, or removed by this theory ; and its 

 principles are illustrated by the progress and conclusions of 

 every well established branch of human knowledge. It is the 

 object of the present chapter to show how it has recently been 

 applied to connect together and explain a variety of curious 

 facts which had long been considered as inexplicable anomalies. 



of the Principle of Utility 

 Perhaps no principle has ever been announced so fertile in 

 results as that which Mr. Darwin so earnestly impresses upon 

 us, and which is indeed a necessary deduction from the 

 theory of Natural Selection, namely that none of the 

 definite facts or organic nature, no special organ, no char- 

 acteristic form of marking, no peculiarities of instinct or of 

 habit, no relations between species or between groups of 

 species can exist, but which must now be or once have been 

 useful to the individuals or the races which possess them. 



