342 University of California Publications in Zoology [Vol. 11 



out and elongated distal angles of the cells. The nuclei in the 

 basal portion of the barbule show quite distinctly. The total 

 length of the distal barbules is about one millimeter, of which 

 the base occupies but little more than one-fourth. 



An excellent description of the interlocking of the barbs by 

 means of booklets and grooves is given by W. P. Pycraft (1893), 

 and to this paper the reader is referred for a very thorough, 

 interesting, and lucid account of one of the most delicate and 

 highly perfected mechanisms to be found in nature. 



Distal to the incision of the feather, the barbs differ in having 

 a deeper ramus, 1.2 millimeters deep at the base, and more 

 nearly equal proximal and distal vanes, the proximal barbules 

 being longer and the distal ones shorter than in the first barb 

 described, they having a length of one millimeter with a 0.6 

 millimeter base, and a length of 0.76 millimeter respectively. 



On the outer vane there is a considerable modification in the 

 form of the barbules. The proximal barbules (pi. 17, fig. 5), 

 of which there are fifteen or sixteen per millimeter, are 

 quite different from those of the inner vane. The base is 

 long and slender with the usual dorsal recurved edge, and a 

 distinct line of nuclei. At the bend the cells become very clearly 

 demarcated, and are produced at the ventral distal angles, giving 

 a sawlike appearance. A short distance beyond, the projections 

 become greatly elongated and curved, and assume a form com- 

 parable with that of the longer barbicels of the distal barbules, 

 some of the best developed ones being almost hooklet-like in 

 form. Toward the tip a few weak barbicels are developed on 

 the dorsal side. This peculiar type of proximal barbule does 

 not occur throughout the outer vane, the ordinary type being 

 found toward the base of the barbs, especially on those near the 

 base of the feather. The transition from one type to the other 

 is easy and rapid, the barbicels being developed in increasing 

 numbers beyond the ventral lobes, which become slightly altered 

 in form to produce the sawlike appearance above described. 

 The dorsal barbicels begin as short, insignificant spines. 

 Throughout the greater extent of the barb there are six or eight 

 barbicels developed, but toward the tip they increase in number 

 up to ten or twelve. 



