336 ALLEN, ‘Afptosochromatism.’ an 
(1) secretion of pigment by the vital action of a pigment secret- 
ing organ, and (2) the transmission of the pigment through the 
structure of a fully matured feather, and hence (according to the 
best histologists) a histologically dead organ. Because an oil or 
a dye can diffuse itself through a skein of yarn or over the external 
surface of a feather, and possibly penetrate its porous structure, 
Mr. Bonhote claims that such experiments “clearly prove that it 
is quite possible for pigment deposited at the dase of a feather 
[just where and in what manner?] to work its way up by purely 
physical means. If an artificial pigment can do this, we need 
have no doubt that it is possible for a natural pigment to do the 
same.” . 
Here, then, is the whole basis of the theory of ‘color-change’ in 
feathers, or ‘ aptosochromatism,’ as set forth by one of its latest 
supporters ; an assumption to my mind, resting : (1) on erroneous 
observation, and (2) on conjecture of what may or ought to hap- 
pen if this belief in ‘colour-change’ were true. Victor Fatio’s 
above cited observations and conclusions, published a generation 
ago, need not awaken much surprise, but it is a matter for aston- 
ishment that they should find supporters in this closing year of 
the nineteenth century. 
Since Mr. Bonhote finds that I have ‘‘adduced no proofs in 
favour of non-colour change” in my paper on this subject pub- 
lished in 1896, it is hardly worth while to discuss the subject 
further in the present connection. In view of such a statement, 
however, I can hardly believe that my critic has given the paper in 
question very careful attention. As the subject is at present 
receiving renewed consideration, I am quite willing to await the 
results of expert investigators in this special line of research, both 
from the histological side and from the standpoint of the student 
of moult and plumage change in general. As Dr. Dwight, who has 
already spent years in the study of this subject, has well said: 
“When the well-established laws of feather growth and feather loss 
fail to account for plumages, it will be time to adopt theories 
demanding new life in epidermal structures, that for many 
months have been histologically dead.” 
