STRONG: DEVELOPMENT OF COLOR IN DEFINITIVE FEATHER. 175 
The number of supposed cases was greatly reduced when it was discov- 
ered that more than one molt may take place in a year, and the recent 
researches of Chapman (’96), Dwight (:00, :00*), and Stone (’96 and 
00), which I can corroborate from my own observations on caged birds, 
have shown that partial molts may take place at various times during 
the year. Changes due to such partial molts seem sufficient to account 
for all forms of color change hitherto attributed to a process of repig- 
mentation. 
I have found no good record of actual solution by natural causes of 
pigments contained in the feather except in the case of the pigment 
turacin. In the great majority of cases, artificial solution is accom- 
plished by chemical reagents with great difficulty. Even if pigments 
were dissolved in the feather, it is inconceivable that they should be re- 
distributed to form the exceedingly constant and often complex patterns 
characteristic of bird feathers. 
Pigmentation takes place, as has been shown, at a very early stage in 
the differentiation of the feather, when the cells composing its funda- 
ment are in an active condition and in intimate relation with sources of 
nutrition. In the case of melanin pigments, there are branched pig- 
ment cells which supply pigment in the form of rod-shaped granules 
directly to the feather fundament. The contention for a flow of pig- 
ment from the barbs into the barbules, etc. (Keeler), is at once made 
absurd by the fact that the barbules are pigmented before the barbs are 
differentiated. 
Variations in color patterns are easily correlated with variations in 
the distribution of pigment in the early stages of the feather’s develop- 
ment. When completed, the feather is composed of cells which have 
been entirely metamorphosed into a firm horny substance and_ its 
pigment is imbedded in that lifeless matter. The cells composing a bar- 
bule are fused into a solid, more or less homogeneous structure. ‘The 
pigment of one portion of the barbule is as effectually isolated from that 
of another as is the coloring of various parts of a piece of agate. Like- 
wise in the barb and rhachis, pigment is definitely and permanently 
located either in the solid cortex or in effectually separated cells of the 
medulla ; and there are no pores large enough to admit the passage of 
melanin granules. The characteristic longitudinal arrangement of 
melanin granules, which one finds at the close of cornification of the 
feather, is permanent. 
The case cited by Krukenberg of a regeneration of the pigment tura- 
cin was unfortunately not described. It seems to me probable that the 
