1916] Chandler: Structure of Feathers 387 



which are of high value from a taxonomic point of view, namely, the 

 number and size relative to the proximal barbules, the form and gen- 

 eral character of the base, the general size and form of the pennulum 

 relative to the base, the number, size, shape, and general characters of 

 the various kinds of barbicels, especially the ventral teeth, ventral 

 cilia, and basal dorsal cilia, and finally, the differences between the 

 distal barbules of inner and outer vane. 



The proximal harhules are far less variable than the distal barb- 

 ules, and as a rule are of much less taxonomic value. Their chief 

 phylogenetic modifications are in the following: size of base relative 

 to distal barbules, and relation of width to length ; number, form, and 

 conspicuousness of ventral teeth ; form of pennulum, and length rela- 

 tive to base J and condition of ventral cilia in barbules near the tip 

 of barbs in the outer vane. 



The chief value of the hody feathers lies in the degree and man- 

 ner of simplification of the barbules from the remex types, and the 

 presence or absence, and form, if present, of flexules. 



The down harhules from the region of the superior umbilicus of 

 remiges and large coverts, and from the less developed portions of 

 barbs of other feathers, e. g., at the tip of the barb, are not always of 

 taxonomic value, but the typical down barbules from a portion of the 

 feather where they reach their highest development, as for instance 

 near the base of the distal vanule of a well-developed downy barb, 

 are of very great value from a phylogenetic point of view; in fact, 

 it is frequently possible by means of the down alone to identify the 

 group to which a bird belongs and unquestionably to determine its 

 relationship to other groups. The characters which are of value are 

 the length, the size and form of the base (of value only in the case of 

 some Coraciiformes and Passeriformes), the character and frequency 

 of the nodes, and the presence or absence of prongs. 



Methods of color production are of more or less taxonomic value 

 in certain cases. For instance, the iridescent colors of ducks and 

 other water-birds are produced differently than in gallinaceous birds, 

 and in both of these differently than in Coraciiform birds. 



3. Relationships of Groups Suggested or Corrohorated 



The morphology of feathers, as presented in the preceding pages, 

 adds one more basis for comparison of different groups of birds, and 

 seems to throw new light on the relationship of certain groups to 

 others. A classification which even comes near to expressing true 



