76 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
reappearance of the normal color after drying was not due to any true 
regeneration, but to the fact that upon drying a physical change had 
taken place in the pigment and that it had not been dissolved. 
When the feather is completed, the dermal pulp possesses no func- 
tional connection with it; the barbs and barbules are then practically 
isolated from the vital processes of the organism and have no further 
power of growth. 
The arguments against change of color without molt through repig- 
mentation or regeneration of pigment may be summed up as follows : 
1. Most feather pigments are too resistant to chemical reagents to 
warrant belief in their solution and redistribution. 
2. Pigmentation of the feather has been observed to take place only 
in the younger stages of the feather germ. 
3. At the end of cornification melanin granules have a definite ar- 
rangement, which is permanent. 
4, When cornification has ensued, the various elements of the feather 
are hard, more or less solid, structures and their pigment contents are 
effectually isolated from one another. 
d. There is no satisfactory evidence of the occurrence of repigmenta- 
tion, and all the histological conditions render such an event highly im- 
probable. 
VII. Summary. 
1. The intermediate cells at the base of the feather germ multiply by 
mitosis, not all of them being derived from the cylinder-cell layer directly. 
2. The barbules are formed each from a single column of cells 
placed end to end. These columns are arranged parallel to each other 
and form the two /ateral plates in each ridge of the feather fundament. 
The lateral plates correspond respectively to distal and proximal sets of 
barbules. The final form of the barbule results from a change in the 
shape of its component cells. 
3. Each of the cells composing the distal half of a distal barbule may 
send out one or two processes, the barbicels. 
4. The barbs are differentiated from cells making up the axial plate, 
and appear later (Figs. 20, 21) than the barbules. On the ventral 
cortex of the barb is often found an asymmetrical ridge, which has its 
apex pointing towards the rhachis, as may be seen in a cross-section of 
the feather germ. The epitrichium described by Haecker as covering 
the cortex, I consider to be only an optical effect. 
5. A basal membrane composed of flattened dermal cells separates the 
