10 GEINEKAL HISTORY OF BIRDS. 



it is very large, nearly if not quite equal in size to the main shaft, and very 

 similar to it in appearance, while the other extreme is represented by the More- 

 pork {Podargus) where the aftershaft is reduced to a mere horny scale without 

 barbs. In Grouse and Quail it is very well-developed, while in song birds it 

 is very small. Aftershafts are never pannaceous, and the barbs are usually 

 separate, except sometimes close to the shaft. 



The second kind of feathers is generally spoken of as down, and down- 

 feathers form an important, though usually concealed, part of the plumage. 

 Down-feathers possess a short quill, but the shaft may be wanting, and is 

 never conspicuous, while the vanes are not recognizable as such, but consist of 

 entirely independent, more or less filamentous barbs. An aftershaft may be 

 present, but it is very similar to the mainshaft. Where no shaft is present, 

 the barbs spring in a tuft from the end of the quill which is so short that the 

 tuft of down is apparently nearly sessile. Down-feathers form a large part, 

 if not all, of the first plumage of most birds, and each contour-feather is pre- 

 ceded by a down-feather. Between down-feathers and contour-feathers nearly 

 all stages of intergradation occur, and many of these intermediate feathers are 

 distinct enough from either to form a new group known as half-down or semi- 

 plumes. Like down, the half-down is concealed by the contour-feathers, but 

 like the latter, it always has a well developed shaft and is more or less penna- 

 ceous near the tip. The fourth group of feathers is made up of those which 

 are called filoplumes. These have the shaft very slender and elongated, and 

 either lack vanes entirely or have them represented by a very small tuft of 

 barbs at the tip of the shaft. They never have an after-shaft. The last group 

 includes a peculiar type of down, which is constantly growing and breaking 

 off at the tips, thus giving rise to a peculiar greasy powder, the use of which 

 is still open to question. Such feathers are called ^wfe^^Zwmes, and they are 

 least common of any of the five groups. 



THE ARRANGEMENT OF FEATHERS. 



The above-mentioned kinds of feathers compose the plumage of birds; 

 very few birds possess the five sorts. Pulviplutnes are found only in a very 

 few cases, except among Herons, where they ai'e specially well-developed. In 

 the Herons, and in most other cases where they occur at all, they are found 

 in special dense patches known as the povider-down tracts. The number of 

 these tracts varies in different species of Heron from 2 to 8. In a few 

 birds, the pulviplumes occur scattered among the contour -feathers, some- 

 times in considerable numbers. Filoplumes occur in practically all birds and 

 generally accompany the contour-feathers. Usually there is one filoplume 

 close to each contour-feather, at least on the neck and rump, and generally on 

 other parts of the body. Sometimes 2, rarely 6, 8 or 10, filoplumes accom- 



