334 ALLEN, ‘ Aptosochromatism.’ a 
that individual feathers themselves change color without being 
moulted. It has been believed by some that Ptarmigans moult 
continuously and in a haphazard way during the whole year. All 
of these ideas have arisen from a misconception of the facts, 
which show that the feathers supposed to be changing color or 
pattern are of that particular color and pattern at the time they 
first expand, and that the continuous moult resolves itself into 
definite periods, and that the feather growth is systematic, differ- 
ing in no respect from that of the rest of the Grouse. The one 
essential difference between the moults of the Ptarmigans and 
those of the Grouse is found in the extra moult in the autumn by 
which the brown feathers regularly assumed at the usual periods 
of moult in both young birds and old are replaced by white 
ONES, ue 
“The plumages of the Ptarmigans are puzzling not only on 
account of the plumage intermediate between summer and winter 
dress, but also on account of the rapidity with which the moults. 
follow each other, one beginning before the previous one is com- 
pleted, and apparently overlapping at some points. Moreover, 
the incompleteness of the partial moults with the irregular reten- 
tion of feathers peculiar to them adds to the confusion of ideas 
resulting from seeing together an assemblage of feathers belong- 
ing to several different stages of plumage. As for the rapidity 
with which one moult treads upon the heels of another, it can 
only be said that the mode of life of the Ptarmigans requires it 
and the activity of the feather papilla is no greater than the 
necessity. As a matter of fact, some papillz produce approxi- 
mately one feather in May, another in July and a third in Septem- 
ber, but there are many which produce but two feathers during 
this period and others only one, while all of them are dormant 
during the long winters.” 
In respect to “the supposition that pigment ca find its way up 
an old and fully-grown feather,’’ Mr. Bonhote assumes that this 
supposition is true, and that, in the season of moult, “ if the fol- 
licle [of a feather] is at that time engaged in producing a mew 
feather, the pigment is placed in it; if not, zt zs drawn up into the 
Jeather which is already full-grown.” This latter affirmation, put 
forth as a statement of known fact, rests entirely upon a series of 
