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 insufificiency 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. 



