The Making of Species 
general acceptance are to be attributed, firstly, 
to their simplicity ; secondly, to the fact that they 
have thrown light on many phenomena which 
previously had seemed inexplicable ; thirdly, that 
if we assume, as the great majority of biologists 
do, that evolution has been effected by the 
accumulation of numerous variations, small in de- 
gree and indefinite in direction, we seemed forced 
either to accept Neo-Darwinism or admit that the 
whole subject of animal colouration baffles us, in 
other words, to reject what appears like cosmos 
and substitute for it chaos. 
With a few exceptions, books that deal with 
the colours of organisms, while emphasising 
the evidence in favour of the generally-accepted 
theories, seem almost entirely to ignore the host 
of facts that do not appear to fit in with them. 
This is largely due to the almost unavoidable 
bias of the human mind when obsessed by a pet 
theory. There are none so blind as those who 
will not see. It is also, in part, the consequence 
of the prevalent neglect of the scientific method 
of comparison which leads men to theorise on 
insufficient evidence. This, of course, is a natural ' 
result of specialisation in biology. Naturalists 
are in the habit of confining their study to the 
habits of the animals of one particular country 
and then making far-reaching generalisations 
therefrom. 
As an example of the kind of theorising to 
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