1916] Chandler: Structure of Feathers 371 



Hydrocorax, but in neither are the barbules as large and heavy. 

 The breast feathers and looser back feathers are of the same type 

 as other coraciiformes, but the barbs are very loose distally, soon 

 giving way to a downy structure. 



Striges. — The owls are characterized by remarkable softness of 

 their plumage, which, as already shown by Mascha (1904), is brought 

 about by an even more remarkable modification in structure of 

 barbules. 



In Buho maximus, on inner vane of remiges, distal barbules 

 (pi. 32, fig. 84a) have base of typical coraciid type, with sinuate 

 ventral contour and small, slender, ventral teeth, but pennulum 

 excessively elongated, frequently reaching a length of over 2 mm., 

 when the base is only about 0.3 mm., being, therefore, nearly seven 

 times as long. The booklets, 5 in number, very slender, increasing 

 in length to a remarkable degree from the proximal to the distal 

 ones. As shown by Mascha (1904), the pennulum is flattened 

 dorso-ventrally and furnished with a complete double series of both 

 dorsal and ventral cilia, which, however, are curved in such a way 

 that their tips project laterally (pi. 32, fig. 84a.). Both dorsal and 

 ventral cilia slender and flexible, the ventral ones, especially on the 

 proximal portion of the pennulum, longer than dorsal ones, the 

 proximal ones of which are not at all enlarged or modified. The 

 proximal barbules (pi. 32, fig. 846) have an elongate, narrow base, 

 long, slender ventral teeth which, however, lie in close juxtaposition 

 and so are inconspicuous, and an exceedingly long filamentous pen- 

 nulum, almost as long as that of the distal barbules. 



On the outer vane distal barbules differ in that pennulum is 

 much stouter and considerably shorter, with the dorsal cilia entirely 

 absent. Proximal barbules have very slender base and long fila- 

 mentous but moderately heavy pennulum with a series of very 

 slender, delicate and inconspicuous ventral cilia. Comblike outer 

 margin of outer vane due to curving back of the rami, with an 

 accompanying shortening and stiffening of the barbules and loss of 

 the interlocking apparatus. Plate 32, figure 84c represents a distal 

 barbule from this region of barb. 



Body feathers of owls resemble remiges in great length of bar- 

 bules. The delicate, semi-transparent character, especially of breast 

 feathers, is due to wide spacing of barbs and barbules, the former 

 set about 15 per centimeter on each side, the latter 8 or 9 and 12 

 to 15 per millimeter on proximal and distal vanules respectively. 



