242



Dr. A. G. Butler,



NOTES ON MELANISM. AND ALBINISM IN BIRDS.


By A. G. Butler, Pli.D.


In a paper published in 1889 ( Proc. Zool. Soc. pp. 282-7)

“ On a New Genus of Fossil Moths from the Eocene Freshwater

Limestone of Gurnet Bay, Isle of Wight,” I discussed the

question as to the development of colour in Lepidopterous

Insects, and the probability that (all forms presumably being

originally either white or black, or a combination of these two

hues), there was strong evidence to show that the first bright

colours produced were blue from black, and yellow from

white.


Furthermore, I argued that white indicated delicacy of

constitution if acquired by reversion, a wild white primrose

which I planted in my garden in the hope of multiplying this

sport, having produced 110 seed, and having died after division

of the root.


Again, in a paper published in ‘‘The Zoologist” for 1902

I made the following remarks respecting albinism in birds (p.

252):—


“ There is no doubt that albinism in birds is due to con¬

stitutional weakness, and is a frequent result of close inbreeding.

If a pair of Sparrows (Passer domesticus) takes up its quarters in

one part of a building, or in the roof of an isolated cottage, the

young, inbreeding for successive generations, are pretty certain

to throw individuals with more or less white in the plumage.

The White Dove (popularly known as ‘White Java’) is known

to be merely the albino form of the Collared Turtle (Turtur

risorius), and Mr. Abrahams assured me that it could always be

produced by close inbreeding from the common type. It is

probable that inbreeding first produced the pied Java Sparrows,

from which the Chinese, by careful selection, evolved the

white variety of that species. White in the plumage of birds

is frequently due to old age, and increases year by year. A

Chaffinch which Iliad for about fifteen years acquired quite white

eyelids before its death, and a Cordon-bleu (Estrilda phoenicotis),

now in my possession, began to acquire a white wing-speculum

some three or four years ago ; this has now become a large white



