308 
COLOUR IN NATURE 
CHAP. 
elaborate discussion of the possible uses of colour, 
for we see that it arises apart from usefulness, and 
ergo may persist apart from usefulness. This is the 
view put forward in the Evolution of Sex, where the 
colours of organisms are regarded as expressions of 
the constitution of the individual. 
3. Mr. Cunningham and Professor Elmer's 
Theories .—Although the theories as to the origin of 
colour, adopted on the one hand by Mr. Poulton, 
and on the other by Mr. Wallace, are widely accepted 
among biologists, dissentients are not wanting, and 
are probably on the increase. Among the older 
theories, that dependent upon the acceptance of 
Lamarck’s factor of an inheritance of acquired 
characters, has been vigorously maintained by Mr. 
Cunningham in this country, and Professor Eimer 
and a numerous school abroad. Professor Eimer’s 
theories of the origin of colours and markings involve 
especially the conception that in this, as in other 
respects, evolution is a progression along definite lines 
determined by laws of growth which are the accumu¬ 
lative result of environmental stimuli ; the emphasis 
is, however, so laid upon the laws of growth that the 
fact that these involve an inheritance of the effects 
of environmental influence is apt to be lost sight of. 
The difference between this and the preceding 
theories is best indicated by a concrete example. 
We may take the vexed question as to the reason 
for the absence of pigment in cave-inhabiting animals. 
According to Mr. Poulton, animals which live in 
darkness are pale, because pigment would not be 
visible in these situations and is consequently no 
longer of any use to them ; it is, therefore, no longer 
