330 ALLEN, ‘ Aptosochromatism. ae 
specimens taken at the proper time of year will verify them. 
Nevertheless, Mr. Birtwell thinks that ‘for good results in investi- 
gations upon color change one should operate rather upon live 
birds in confinement.’ Well, perhaps so, for the ‘ proof’ of color 
change without moult certainly does rest chiefly upon caged birds. 
The fact that they moult irregularly and often at long intervals 
and, as for instance in the Purple Finch (Carpodacus purpureus) , 
having once lost their bright colors may never regain them does 
not seem to impair belief in a theory fifty years or more old. It 
began when most people were ignorant of the fact that birds could 
and did moult twice in the year. This was sagely declared to be 
too great a drain upon their vitality; but when it was found that 
some species did moult twice, theory had to be reserved for others 
that did not appear to be guilty of draining their vitality. When 
these in turn were proved to moult twice refuge was taken in 
the assumption that only certain individuals of certain species 
changed color without moult. Later came red-handed proof of 
guilt in feathers found growing upon these individuals and the 
believers in theory fell back upon the claim that although one 
feather did seem to be renewed by moult, the one next to it 
underwent a color change, concerning the nature of which no two 
believers were agreed. Some of them have gone so far as to 
assert rejuvenation of frayed edges by some sort of exudative 
processes which only need to be carried a step farther to elimi- 
nate altogether the necessity of moult. This is no fancy picture 
and I only paint it that my readers may know what ‘ aptosochrom- 
atism ’ represents.” 
Referring more directly to Mr. Birtwell’s article, Dr. Dwight 
remarks: ‘ An observer who did not know the plumage differ- 
ences between the adult and the young bird, nor discover the 
structural differences between autumnal and nuptial feathers, nor 
hesitate to look for ‘ carrier pigment cells’ under the microscope, 
may well have his accuracy of observation questioned..... When 
the well-established laws of feather growth and feather loss fail to 
account for plumages, it will be time enough to adopt theories 
demanding new life in epidermal structures, that for many months 
have been histologically dead. The existence of such a thing as 
‘aptosochromatism’ will hardly be proved by those who have no 
