let BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
fluid can be colored, its progress noted, and the feather stained intra 
vitam. Soon after death this becomes no longer possible. To see the 
stain the microscope is usually necessary. Call this ‘ osmosis,’ ‘ capil- 
larity,’ or what you please, it is none the less a vital process in that it 
ceases soon after death, and must be studied in the fresh feather. 
(c) The broken tips of the rays forming the vanes are, when fresh, 
capped by a mass of the fluid, which has escaped, leaving the part 
immediately below the stump pale from the loss of the fluid pigmented 
matter. (d) In museum skins this fluid matter gradually dries and by 
its consequent increase in density, and that of the feather tissue, the 
colors darken: while the freshness and gloss of life disappear.. (e) The 
evanescent tints of some species,—notably the fading of the rosy 
‘blush’ of some of the Terns, soon after life is extinct, is due to the 
drying up or escape of this fluid, while the lost tint was due to the 
physical effect of structure, the shrivelling and change of form would 
act on the light rays and the former colors would be lost in conse- 
quence. Comparisons of specimens of Sterna paradisea, 8. dougalli, 
and other Terns in my collection, showed that examples having the 
‘blush’ most marked are those in which the feathers are least dry.” 
Chadbourne (’97*) has described the case of a canary * which was sup- 
posed to have changed under the influence of being fed with red pepper 
to the reddish yellow color which, as is well known, may be pro- 
duced at the time of molting. It was clearly demonstrated by Sauer- 
mann (’89), however, that in the birds experimented on by him the 
color is not altered unless the special feeding is carried on while the 
feathers are in process of development. This I have found to be also 
the testimony of bird fanciers. 
Though it is probable that the oil supplied by the uropygeal gland is 
a factor in the production of color effects, especially in giving gloss or 
lustre, it is unreasonable to suppose that the feather itself produces or 
gives forth any of the oil found upon it. Although the feather struc- 
ture is slightly permeable by liquids, as Fatio observed, it does not fol- 
low that the pigment imbedded or diffused in its horny substance is able 
to flow about. 
There is no satisfactory evidence of the occurrence of repigmentation. 
1 Dr. Chadbourne has explained to me that there was a misunderstanding in 
the case of the canaries he mentioned. ‘They were not kept by him, but were in 
the possession of the janitor of the Harvard Medical School, who tells me that the 
changes mentioned by Dr. Chadbourne were produced only by feeding at the time 
when the feathers were developing. 
LK ee Oe ee eee 
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