172 The Field Naturalist's Quarterly Aug. 



an elongated structure with a hollow stalk — the quill or 

 calamus, and an expanded distal portion — the vane or 

 vexillum. At the bottom of the quill is an aperture called 

 the umbilicus inferior, into which fits the small prolonga- 

 tion of the skin — the feather papilla. There is another 

 much smaller aperture at the junction of the quill and the 

 vane on the inner side of the feather — i.e., next to the 

 body of the bird. 



A small tuft of down at the top of the quill represents 

 the after-shaft of some birds. The vane has a mid-rib or 

 shaft, the rachis, which is a continuation of the quill, but 

 is different from the latter inasmuch as it is solid. On 

 each side of the shaft there is a kind of membrane, form- 

 ing that part of the feather which is expanded, and which 

 is composed of flattened and expanded plates, called 

 " barbs." On the sides of these barbs there are small 

 processes or " barbules," which have much the same re- 

 lation to the barbs as the barbs themselves to the shaft. 

 Thus a feather is able to present a continuous surface for 

 flight or other purposes. A simple way of demonstrating 

 this is to rub the finger and thumb down a feather from 

 the tip, when the barbs will separate, and then by revers- 

 ing the process the barbs will regain their normal position. 

 The exact way in which the barbs interlock can be made 

 out only under the microscope, though the barbules can 

 be seen with the aid of a pocket-lens. Under the micro- 

 scope there will be seen — in addition to the barbules — a 

 further series of booklets or " barbulets " extending from the 

 lower edge of the anterior barbules. These booklets inter- 

 lock with the posterior barbule immediately below them. 



Sometimes a second shaft, called the "after-shaft," may 

 spring from the top of the quill, and is usually a small 

 representation of the ordinary shaft wdth its vane. In 

 some feathers the after-shaft is always wanting, as in the 

 wing and tail feathers ; while in some birds which possess 

 an after-shaft to some of their feathers it is as large as 

 the feather itself. A number of species of the great order 

 Galli, or Game Birds, possess after-shafts, while numbers 

 of birds do not. 



Feathers, like scales, arise in the embryo from papillae 

 of the skin, formed of dermis with an epidermal cover- 



