56 INHERITANCE IN POULTRY. 



occasionally exhibited. Frizzling is probably morphologically related to 

 " rough coat " in mammals. The frizzled characteristic is a typical sport. 



The Silky fowl (fig. 43) is likewise of great antiquity. Marco Polo saw 

 it in Asia in the thirteenth century (teste, Diirigeu, 1886, p. 298). Gesner 

 described it in 1555. It is a native of eastern India, coming, according to 

 Blyth (Tegetmeier, 1867, p. 221), from China, Malacca, and Singapore. A 

 condition allied to silkiness (described below at page 57) is found in other 

 races of poultry, particularly, as the following statements show, in the 

 Cochins. 



Tegetmeier (1867, p. 46) says : 



The singular variety known as Silky Cochins, or sometimes as Emu fowls, is simply 

 an accidental variation of plumage which occasionally occurs and which may be perpetu- 

 ated by careful breeding. The cause of the coarse fluffy appearance of these remarkable 

 fowls is to be discovered in the fact that the barbs of the feathers instead of being held 

 together by a series of hooked barbules (so as to constitute a plane surface, as occurs in 

 all ordinary feathers) are perfectly distinct, and this occasions the loose fibrous silky 

 appearance from which the fowl obtains its name. 



An engraving of such a feather is given by that author at page 224. 



Wright (1902, p. 255) states that he has seen no Emu fowl "now for 

 twenty years," and makes the suggestion that this entire "silkiness" of 

 feather is the extreme limit, perhaps, of the kind of plumage which gives 

 fluffiness to the leg region of American Buff Cochins. 



The fluff of Cochins and Brahmas has indeed many points of similarity in 

 structure with the feathers of the Silky. In one feather from the abdomen 

 of a Brahma hen, whose shaft is 35 mm. long, I find the barbs very long (up 

 to 30 mm.) and not connected together. Each barb bears, proxirnally, two 

 rows of short, flat, hook-shaped barbules alike on the two sides. Beyond, 

 there are a few short barbules that taper to a hair-like apex. Still more 

 distally on the barb the barbules may attain a length of 5 mm. , be altogether 

 devoid of booklets, but show a segmented condition as in the Silky Far 

 from my preconceived notion, I find few intergrades between the short barb- 

 ules and the others. The more proximal of the long barbules are the longest 

 of all, and the short barbules (which rarely exceed 0.5 mm. in length) also 

 occur here scattered among the long ones. There thus seems to be a dis- 

 continuity between the two kinds of barbules, and this harmonizes with the 

 view that the long barbule is a mutational form of the more typical short 

 barbule. 



As to the relation of the plumage of the Silky fowl to the fluff of Cochins, 

 I have formulated the following hypothesis : Long and short barbules are 

 two dimorphic forms found among birds. This dimorphism has been recog- 

 nized in the terminology "down feathers" and "contour" + "quill" 

 feathers. Down feathers may or may not have a shaft ; they have barbs, 

 and usually barbules, the latter being long and devoid of cilia or hooklets. 

 In the contour and quill feathers of most birds the short barbules alone are 



