Ill 
MIMICRY, AND OTHEK PROTECTIVE RESEMBLANCES AMONG 
ANIMALS 1 
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. 
