on development of pattern in birds.



185



violet or lilac markings frequently appear in contiguity therewith.

In birds crimson is commonly found in juxtaposition to black, or

even (as in the Gouldian-finch) taking the place of black ; but, as black

represents a combination of all colours, there seems no reason

why it should be restricted in its development, as white must

needs be.


White is the absence of all colour, and the first step it takes

towards colour-development is to yellow.* In at least one moth which

passed through my hands in my old Museum days, there were both

pure white and bright yellow individuals; and in some of the butter¬

flies of the genus Terias the males are yellow but the females pure

white, indicating that the brighter hue was due to sexual selection,

or, less probably, to superior vigour in the male sex; since white,

unless acquired for protective purpose, is generally an indication of

constitutional weakness.


Well, in all these matters we are profoundly ignorant; we

need ever more and more evidence. As dear old Darwin used

to say, when some useful new fact was brought to his notice :

“ God bless my soul, how little we know ! ” That must continue

true of mortal man, but we ought always to be growing in know¬

ledge ; it is the chief object of all study; therefore I hope some

of our members will do their best to let in the light upon the origin

of bird patterns.


[In connection with Dr. Butler’s remarks on colour patterns,

we may mention the poecilomeres, or colour areas, which have been

mapped out by Messrs. Dewar and Finn. These occur on the

chin, malar area, upper jaw, a small patch above and slightly in

front of the eye, and another below and slightly behind the orbit.

Other poecilomeres are the ear, crown of the head, and occiput; on

the body they are found on the fore-end of the sternum, vent, and

rump ; they also occur above and below the shoulders, and on the

wrist and thighs.


Colour mutations, when present, are found on these areas.

White feathers originate from poecilomeres; so does excessive



* [Similarly in the human race yellow has been shown to be the next stage to pure

albinism : the eyes of these human lutinos are blue. See Prof. Karl

Pearson’s monograph on “ Albinism in Man.”—G. It.].



