Ne ALLEN, ‘ Aptosochromatism. 329 
changed feathers were found in an embryonic condition at any 
time, although frequent careful examinations of the bird were 
made.” This, as will be noted later, is, taken altogether, a fine 
exposé of Mr. Birtwell’s ignorance of what normally occurs in 
respect to color change without moult, or by simple normal 
abrasion. He goes on to say that in feathers examined under the 
microscope in January and February he “could detect no pres- 
ence of carrier pigment cells and found the calamus of each 
feather to be in the expected dried up condition. The change 
would thus seem to be confined to activity in the feathers 
alone.” (!) 
His conclusions from this study are: “ (1) that Aptosochroma- 
tism in my /asserina cyanea occurred beyond doubt, (2) that 
although present with severe feather loss it does not follow that 
the gain of color was directly responsible to it, as proved by 
careful examination of the newly acquired feathers, and (3) that 
although the feather loss was objectively independent of the 
Aptosochromatic change, it might subjectively be so, inasmuch 
as old and imperfect feathers were renewed for active and healthy 
ones, in which such a color change subsequently occurred.” 
Dr. J. Dwight, Jr., in a later number of ‘Science’ (April 30, 
1900, pp. 627-630), under the title ‘The Plumage and Moults of 
the Indigo Bunting,’ reviews Mr. Birtwell’s paper at some length, 
describing in detail the successive stages of plumage of this bird, 
and criticising with some sharpness the class of work Mr. Birt- 
well’s paper so characteristically illustrates. After quoting some 
of Mr. Birtwell’s comments on the attitude of the opponents of 
the theory of ‘ Aptosochromatism, ’ transcribed at the beginning of 
this review, in which he says “they cling to their belief with a 
tenacity wonderful to behold,” Dr. Dwight says: ‘“ Doubtless it 
does seem ‘ wonderful’ to persons who would wave aside all the 
careful observations that have been made upon feather growth 
and feather wear, and plumage generally, but possibly it is not so 
wonderful as the strange things they see just as soon as they 
watch a bird of striking colors in a cage.” Dr. Dwight also 
indulges in some comment on the general subject. After his 
account of the changes of plumage in the Indigo Bunting, he says: 
‘* Here then we have the facts about the Indigo Bunting, and any 
