302 
COLOUR IN NATURE 
CHAP. 
which they live, that they can only be distinguished 
with difficulty. If the enemies of such species are 
psychologically similar to ourselves, the colouring 
must render them less conspicuous to these enemies, 
and must thus be protective. Therefore it may be said 
that, however the colour in these cases first arose, it 
must always have been, other things being equal, 
useful to the species ; therefore the forms displaying 
these colours would tend to persist, the others would 
tend to be eliminated ; therefore we may say that the 
colour arose by Natural Selection, which weeded out 
all those not possessing it. 
This is in essence the explanation of colour 
phenomena given by a great number of naturalists at 
the present time. Colour they say is originally non¬ 
significant, a result of the chemical or physical 
properties of substances ; its appearance in the super¬ 
ficial tissues may render the organism better fitted 
to survive in the struggle for existence, and therefore 
is encouraged and maintained by Natural Selection. 
The various types of coloration presumed to be of 
use have been classified under the headings of 
Protective Resemblance, Mimicry, Warning Colours, 
and so on ; their use is supposed to be to protect 
the organism from its enemies, to enable it to steal 
unperceived on its prey, or to warn its enemies that 
it is unpalatable or dangerous and must be avoided. 
Beside these, however, there is another series of 
colours to be considered. We have already seen 
that in birds the males are frequently far more 
brilliantly coloured and ornamented than the females. 
As these colours do not fall into any of the divisions 
already mentioned, many naturalists have adopted 
