1916] Chandler: Structure of Feathers 341 
ringlike form (pl. 36, fig. 108c). Some of these rings frequently, 
in fact almost always to a greater or less extent, break loose from 
the nodes, and slide along on the slender, filamentous barbule like 
rings on a wire, sometimes breaking up into groups of 5 or 6. It is 
possible to move them along on the barbules by placing them on a 
slide and moving the cover glass. Toward the tip of the barbules 
the ringlike structure is again lost, and the nodes become simply 
swollen. On the proximal vanule these rings are usually not so 
perfectly developed, and on the more distal portion of both vanules 
the nodes become simply swollen, and shaped more or less like a 
eucalyptus seed, with short prongs, or the barbule becomes almost 
smoothly filamentous, with indistinct nodes. The outside diameter 
of the rings in Meleagris virginiana, for instance, is about 0.012 
mm., while that of the internodes of the barbules is only 0.004 to 
0.005 mm. The down at the base of remiges and rectrices, and that 
of the aftershafts, never possess the ringlike structure. The downy 
structure varies very little in any of the families of the suborder. 
d) Color Modifications 
There are many interesting color modifications in this group, 
especially in the Phasianidae, but they can only briefly be discussed 
here. White is usually produced by diffusion of light merely from 
translucent barbules, but in Lagopus the barbules (pl. 24, fig. 47a) 
are filled with minute bubbles which tend further to diffuse the 
light. Deep glistening red, yellow, and orange colors are usually 
produced by pigmented, highly polished barbs which are naked, or 
possess much reduced barbules. Changeable metallic lilacs, fiery 
reds, blues, greens, and purples are produced by highly refrangent, 
simple, rodlike barbules, the silvery blue feathers of Phasianus 
torquatus, for example, being a result of the combination of white 
barbs with rodlike blue barbules. In the coherent green vanes of 
the tail feathers of roosters, and other similar feathers, the pennula 
of the distal barbules (pl. 24, fig. 429) are responsible for the color 
as in the Anseres, the individual cells, however, not being demarcated 
by constrictions, but the whole pennulum in the form of a curved, 
spoonlike structure (pl. 24, fig. 42/). 
There is a very unusual condition found in the blood-red breast 
feathers of the golden pheasant, where the barbs are closely appressed 
and brought to lie almost parallel with the shaft. In these feathers 
two barbs frequently fuse to form a single one at a short distance 
