1916] Chandler: Structure of Feathers 341 



ringlike form (pi. 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 Lag opus the barbules (pi. 24, fig. 47 a) 

 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 (pi. 24, fig. i2g) 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 (pi. 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 



