INTRODUCTION 27 



these points I cannot agree with either Romanes or Wallace. 

 I do not consider that the display is the strongest argument 

 in favour of Darwin's theory, and I think the effect on the 

 females is perfectly obvious. Wallace argues that the dis- 

 play and gestures of the male, in the case of birds, for example, 

 may be due to general excitement, pointing out that moveable 

 feathers are habitually erected under the influence of anger 

 and rivalry to make the bird look more formidable in the 

 eyes of antagonists. The display and erection of organs or 

 appendages present only in the males according to this 

 argument is no proof of competition or of selection on the 

 part of the females, no proof that the most adorned males 

 accomplish the act of reproduction while the least ornamented 

 fail to beget offspring. 



The more brilliant colour and excessive development of 

 certain feathers or other appendages, being due according to 

 Wallace to the exuberant health and vigour of the males, the 

 question arises how is it that the more vigorous development 

 does not extend equally to all parts and appendages of the 

 body, instead of being confined, as it is very precisely, to 

 particular parts or appendages ? To explain this fact 

 Wallace adopts the theory expounded by Mr. Alfred Tyler 

 in his book on Coloration of Animals and Plants (1886). 

 Mr. Tyler maintained that diversified coloration follows the 

 chief lines of structure and changes at points, such as the 

 joints, where function changes. Mr. Wallace maintains that 

 the enlarged plumes of male birds are situated at points 

 where the nerves and blood-vessels converge. Thus, in his 

 book entitled Darwinism he states that Mr. Beddard ex- 

 amined for him the anatomical relations of the roots of the 

 great tufts of golden feathers in the bird of paradise, and 

 found that they were situated just above the point where the 

 arteries and nerves for the supply of the pectoral muscles 

 leave the interior of the body. But, as Professor Lloyd 



