154 Correspondence.


forty, are marked with ink or otherwise, and carefully measured in

millimeters, in situ, — both as to extent of white and ashy portions, and

then re-examine them from time to time, the secret must be revealed.


I hold if the question is worth a moment's thought or work, it

deserves study, — exhaustive and minute enough to settle it one way or the

other, once and for all.


I should be indeed glad if Mr. Bonhote also would follow out the

above methods of proof, or others as accurate, this spring and let his

results be the " thrashing out" which the Editor so heartily and commend-

ably invites.


The possibilties of wear in the winter feathers are well shown in one

of my Larus ridibundus, in which, judging from a superficial examination

just made, few or no feathers, even at this date, have a normal distal outline,

the barbs showing a symmetrical wear, while, especially on the crown and

upper nape, so many of the proximal barbs are worn away, that the feathers

present the appearance of laterally compressed palm trees, — long naked

shafts surmounted by a few ragged barbs. In each specimen about thirty

early feathers iof the dark spring moult are already in evidence, having

pushed out the winter feathers, measuring from two to five millimeters. If

the winter feathers should prove, (as do the new hood feathers, vide my

article, p. 455) to be subject to an unusual loss of white tips at a certain

time (in the case of the old winter feathers just before they are loosened and

pushed out by the new feathers), the exposure of the distal sooty coloring,

increasing in amount from the forehead feathers back to those of the nape

would result in exactly the increase of area of darker color, as described

by Mr. Bonhote.


But I offer this as tentative and all subordinate to the coming proof,

which Mr. Bonhote or anyone with a captive Gull, a microscope and an

open, unprejudiced mind can undertake.


The radical and (speaking from the standpoint of one moult to the

next) almost immediate change in color of the whole plumage of birds

subjected to new conditions of humidity and abnormal environment which I

am obtaining and shall soon publish, have made me sceptical of evidence

based on one or more feathers in the skins of dead birds. This and other

related problems require continuous and minute examination of the living

bird.


I think that most ornithologists will agree with me, that no more

skilful and thorough study of colour in plumage has been made than that

of Dr. R. M. Strong, of Chicago University, in his " Development of Color

in the Definitive Feather," {Bulletin of the Museum of Comparative Zoology

oj Harvard. Vol. XL., No. 3).


The following is taken from page 176 :


" The arguments against change of color without moult through

repigmentation or regeneration of pigment may be summed up as follows :



