Ill 



MIMICRY, AND OTHER PROTECTIVE RESEMBLANCES AMONG 



ANIMALS 



THERE is no more convincing proof of the truth of a com- 

 prehensive theory than its power of absorbing and finding 

 a place for new facts, and its capability of interpreting 

 phenomena which had been previously looked upon as un- 

 accountable anomalies. It is thus that the law of universal 

 gravitation and the undulatory theory of light have become 

 established and universally accepted by men of science. 

 Fact after fact has been brought forward as being apparently 

 inconsistent with them, and one after another these very 

 facts have been shown to be the consequences of the laws 

 they were at first supposed to disprove. A false theory will 

 never stand this test. Advancing knowledge brings to light 

 whole groups of facts which it cannot deal with, and its 

 advocates steadily decrease in numbers, notwithstanding the 

 ability and scientific skill with which it may have been 

 supported. The great name of Edward Forbes did not 

 prevent his theory of " Polarity in the distribution of Organic 

 beings in Time " from dying a natural death ; but the most 

 striking illustration of the behaviour of a false theory is to 

 be found in the " Circular and Quinarian System " of classi- 

 fication propounded by MacLeay, and developed by Swain- 

 son, with an amount of knowledge and ingenuity that has 

 rarely been surpassed. This theory was eminently attract- 

 ive, both from its symmetry and completeness, and from 

 the interesting nature of the varied analogies and affinities 



1 First published in the Westminster Review, July 1867 ; reprinted in 

 1870 with additions and corrections. 



