254 University of California Publications in Zoology [Vol. 13 



Ventral Teeth (figs. D and E). Anteriorly projecting, ventral, basilar bar- 

 bicels of both distal and proximal barbules of nearly all birds, often 

 lobate or leaflike in distal barbules, usually toothlike in proximal bar- 

 bules. Synonym: toothlike processes (Wray, 1887); ventral lobes 

 (Mascha, 1905). German synonym: ventrale Lappen (Mascha, 1904). 



Flexules (pi. 17, fig. lOe). A new term used to designate the curved bar- 

 bicels occurring on the dorsal edge of the bases of distal and proximal 

 barbules of the trunk feathers in some groups of birds (see p. 272). 

 Hitherto apparently unknown. 



Nodes (fig. F). The junction of the cells of the pennulum of down bar- 

 bules, usually characterized by swellings or outgrowths of some sort. 



Pkongs (fig. F). Short, spiny outgrowths at the nodes of the down of 

 many birds, differing from other barbicels in that three or more may 

 occur on the distal end of a single cell, whereas there are never more 

 than two cilia or other kinds of barbicels on a single cell. 



V. Methods 



After experimenting with various methods of preparing feathers 

 for microscopic study, especially the barbules, it was found that in 

 most cases the examination of dry mounts of barbs' and barbules 

 gave entirely satisfactory results. This was at the same time so 

 simple, and took so little time in preparation, that it was possible 

 to examine the microscopic structures of the feathers of a very large 

 series of birds, and thereby to determine with considerable precision 

 the constancy and uniformity of characters in various groups. 



The barbs were first studied under the microscope with their 

 vanules intact. The vanules were then spread backward in order 

 to separate the barbules for individual study, this being done by 

 merely drawing the barb, tip first, between the thumb and forefinger. 

 With a scalpel some of the barbules from each vanule were scraped 

 off from the region of the barbule which it was desired to study, 

 and mounted dry under a cover glass. In this way a considerable 

 number of individual barbules could be separated, and as they would 

 lie in all sorts of positions, their general form could be studied 

 readily from such a preparation. The morphology of heavily pig- 

 mented structures, could be studied more easily when mounted in 

 balsam. In some cases also barbules were mounted in balsam in 

 order to determine whether certain appearances were due merely 

 to pigmentation, or to structural modification, and to determine 

 the effect of oils of low refractive index on color-producing mechan- 

 isms. The methods of treating individual birds and groups of birds 

 to determine their epiphyologic characters will be discussed at the 

 beginning of Part II. 



