332 



OSCAR RIDDLE. 



erest conditions which a bird can encounter and endure. In types 

 i and 2, the barbs and shaft are often bent or kinked in the ab- 

 normal region. 



The third type of defect is something very much less conspic- 

 uous than either of the two types just considered. It cannot be 



represented in a drawing. It is 

 a very minute depression or dif- 

 ferentiation of some sort extend- 

 ing across the surface of the 

 feather in exactly the same direc- 

 tion as do the defective areas of 

 type i. It is not always easy, 

 however, to determine that it is a 

 depression at all. • It often seems 

 to be a line, or simply a point 

 of union of the distal with the 

 proximal part of the feather- vane. 

 This line is sometimes so incon- 

 spicuous that even close obser- 

 vation may not reveal it. It is 

 probable that these lines are not 

 always depressions ; but, that dif- 

 erences in light-reflecting power 

 exist between a point in such a 

 line and points anterior and pos- 

 terior to it, is unquestionable. 

 Fig. 2. Abnormal region of a plume Jfe term <«lj ne " i s moreover, 

 from an ostrich chick (kindly sent to me . . . . r 



u -d <■ r\ a \ e u u * n °t a thoroughly satisfactory 



by rror. Duerden). a, fault-bar, type fa J J 



2, in which shaft only is present. This One, for, that these defects inter- 

 region shows also a great reduction of the g ra de with others of appreciable 



pigmentation of the shaft. X 4- • i^i ■ l. • <-r>i v 



rfa zvidtli is certain. Ihese lines are 



thoroughly characteristic of the feather and are properly classi- 

 fied among feather defects, for it is at such joints that defects 

 like those of types I and 4 appear. 



Many feather-vanes show at certain points in their length very 

 deep depressions or constrictions which give to them a wavy ap- 

 pearance. At first sight such modifications have nothing in 

 common with types I and 3, but closer study proves that they 



