324 
COLOUR IN NATURE 
CHAP. 
most strikingly. The two papers which have been 
chosen to represent the two positions in regard to 
the matter illustrate at least the main fact that both 
parties are somewhat stronger in attack than in 
defence. It would be easy to multiply references 
almost indefinitely, but this would in large part 
involve mere repetition. The advocate of the 
Allmacht of Natural Selection reiterates in many 
tones the well-established facts of colour resemblance, 
and the insufficiency of laws of growth, of correla¬ 
tion of parts, and the rest to account for these. 
His opponent returns to the charge again and again, 
well armed with the lack of evidence, the absence of 
experimental verification, the disproof of particular 
cases ; there are weak places in the walls of both 
citadels, but both parties are strong in attack ; all 
the clamour has not, however, as yet caused the 
walls of either Jericho to fall. 
To drop the metaphor, it must be obvious from 
the above discussion that there are great difficulties 
in the acceptance of Natural Selection as the most 
important factor in the evolution of colour, and that 
there is little doubt that its aid has been invoked in 
far too reckless a fashion. At the same time, it 
must be confessed that there is not as yet in the 
field a complete and cogent theory which is capable 
of dispensing with Natural Selection ; whether this is 
due to ignorance of physiology, or to the real import¬ 
ance of this factor must be left to the future to 
decide. 
