Note C to Page 394. 449 



facts. When applied to the animal kingdom as a whole, the 

 theory is worthless; and even within the limits of mammals, 

 birds, and insects— which are the classes to which Mr. Tylor 

 mainly applies it — there are vastly more facts to negative than 

 to support it. This may be at once made apparent by the 

 following brief quotation from Prof. Lloyd Morgan : — 



It can hardly be maintained that the theory affords us any adequate 

 explanation of the specific colour-tints of the humming-birds, oi the 

 pheasants, or the Papilionidae among butterflies. If, as Mr. Wallace 

 argues, the immense tufts of golden plumage in the bird of paradise 

 owe their origin to the fact that they are attached just above the 

 point where the arteries and nerves for the supply of the pectoral 

 muscles leave the interior of the body — and the physiological rationale 

 is not altogether obvious, — are there no other birds in which similar 

 arteries and nerves are found in a similar position ? Why have 

 these no similar tufts ? And why, in the birds of paradise themselves, 

 does it require four years ere these nervous and arterial influences 

 take effect upon the plumage ? Finally, one would inquire how the 

 colour is determined and held constant in each species. The difficulty 

 of the Tylor- Wallace view, even as a matter of origin, is especially 

 great in those numerous cases in which the colour is determined by 

 delicate lines, thin plates, or thin films of air or fluid. Mr. Poulton, 

 who takes a similar line of argument in his Colours of Animals 

 (p. 326), lays special stress on the production oi white (pp. 201-202). 



As regards the latter point, it may be noticed that not in any 

 part of his writings, so far as I can find, does Mr. Wallace allude 

 to the highly important fact of colours in animals being so 

 largely due to these purely physical causes. Everywhere he 

 argues as if colours were universally due to pigments ; and in 

 my opinion this unaccountable oversight is the gravest defect 

 in Mr. Wallace's treatment both of the facts and the philosophy 

 of colouration in the animal kingdom. For instance, as regards 

 the particular case of sexual colouration, the oversight has pre- 

 vented him from perceiving that his theory of '" bril.iancy " as 

 due to "a surplus of vital energy," is not so much as logically 

 possible in what must constitute at least one good halT of the 

 facts to which he applies it — unless he shows that there is some 

 connection between vital energy and the development of stria- 

 tions, impribonment of air-bubbies, &c. But any such connection 



* Gg 



