Wee ALLEN, ‘ Aptosochromatism. 333 
Apropos of Dr. Chadbourne’s paper on the Bobolink, Mr. 
_Bonhote says: ‘‘ The Bobolink is not the only bird in which the 
assumption of the breeding plumage varies in different individ- 
uals. From the head of Larus ridibundus 1 have taken at the same 
time new brown feathers and old feathers in process of change, 
while in other individuals there has been a pure colour-change. 
The Ruff is an instance of the change going on in /wo different 
ways simultaneously. The Ptarmigan, again, is another instance, 
and from the examples of this species which I have examined I 
think it doubtful whether it assumes any one of its plumages in a 
uniform manner. The fact that a bird will assume its breeding 
plumage in some feathers by a change of colour, and in others 
by a change of feather, /eads to the supposition that pigment cam 
find its way up an old and fully-grown feather. It does not seem 
to me unlikely that, at a certain season, pigment — which is chiefly 
a waste product, more abundant, on account of the extra energy 
expended, at the approach of spring — should be deposited in the 
follicles of the feathers. If the follicle is at that time engaged in 
producing a vez feather, the pigment is placed in it; if not, 7 zs 
drawn up into the feather which ts already full grown”! 
This quotation shows fairly Mr. Bonhote’s position. Respect- 
ing the portions here placed in italic type, I beg to offer a few 
words of comment. First, as to the Zarus ridibundus, it seems 
strange that I have never been able to detect, in any of the large 
number of specimens I have examined of its closely allied con- 
geners, any “old feathers in process of change,” but always, in 
birds taken at the proper season, plenty of new black feathers in 
all stages of growth. As to the Ptarmigan, I would call Dr. Bon- 
hote’s attention to Dr. Dwight’s paper in the April number of this 
Journal, published before Mr. Bonhote’s paper appeared. Dr. 
Dwight’s whole article on ‘The Moult of the North American 
Tetraonide ’ (Auk, XIII, 1900, pp. 34-51, 143-166), I hope will 
be not only, read, but most critically studied by all who share Mr. 
Bonhote’s views on ‘colour-change.’ Says Dr. Dwight (Z ¢., pp. 
147, 149): “The study of this material [just previously enumer- 
ated], amounting to nearly two hundred specimens, now enables 
me to explain the parti-colored plumages of these birds, a matter 
that has long baffled investigation and given rise to a belief 
