Family and Generic Differentiation. 321 



Before coining to the more practical side c£ the subject, it 

 will be necessary to consider it from a general point of view, 

 by way of clearing the ground and of trying to demonstrate 

 how fundamentally important and how deep-seated colour- 

 pattern is — that it is not the superficial and negligible 

 character which it is generally held to be, and that the 

 factors of environment play but a comparatively small and 

 indirect part in its existence. The first point, then, which I 

 should like to lay stress on is : 



(1) The distinction which must be made between "•colour- 

 pattern '^ and mere coloration. 



It will probably be generally admitted that there is a 

 very great difference between the two. Colour-pattern 

 (that is to say, a certain definite and more or less con- 

 stant relation of colour-factors to certain definite areas of 

 the contour-plumage, occurring through a series of species 

 or genera) implies something of a deeper import than 

 mere coloration — something which from its constancy and 

 persistency, its independence of mere environmental or 

 climatic influences, and its correlation with faunal or geo- 

 graphic areas, appears to undoubtedly suggest the influence 

 of the germ-plasm. If this is so, it obviously follows that 

 the factor of colour-pattern must be of genetic importance. 

 It is heritable. It ought to be, as I believe in many cases 

 it is, a useful phylogenetic guide or clue. 



Mere coloration, ou the other hand, may, I suggest, be 

 regarded as somewhat akin to mere homoplastic variations 

 or convergent adaptations in the deeper realms of mor- 

 phology. Regarded in this sense, mere coloration of this 

 kind is of no genetic value. Again, mere shades and tones 

 of coloration, from the fact that they are the result of direct 

 environmental eff'ects or possibly, in some cases, of simple 

 isolation, and moreover are often simply adaptative or pro- 

 cryptic, have likewise no genetic value. They appear to be 

 exogenous in origin, physiological, ontogenetic and non- 

 heritable. It hardly seems worth while to labour these 

 points, but I must give an example or two to clear the 

 eround. 



