of a Typical Pennaceous Feather. 421 



and adaptive organization of these parts^ have made me think 

 that it might be worth while to publish the results of my 

 work^ founding my remarks upon the embodiment of it in 

 the model which is in the Natural History Museum. 



Figure 1 represents the main part of the model, and shows 

 the inter-relation of the different parts. 



Figures 2 and 4 represent part, modelled separately, 

 showing the different details. 



Figure 3 shows appearances which are indicated on the 

 model (fig. 1), but cannot be shown in the drawing. 



The model was made in gutta-percha, and modelled from 

 nature, the feather selected being a greater wing-covert of a 

 Goose. 



Taking the parts in order, tlie stem of the feather gives off 

 on either side the barbs, and they in turn the barbules, 

 which are termed distal and proximal according as they 

 originate from the side of the barb nearest the tip or the base 

 of the feather. The barbules cross one another at an angle, 

 and are especially modified to give consistency to the vanes. 

 It is this adaptation the model was designed to show. 



The proximal and distal barbules differ totally in form. 

 The proximal barbules are (as shown in fig. 2) thin laminae 

 with a thickened upper edge forming a small ledge or kind of 

 flange (fig. 2, 1) ; the broad end is the one attached to the 

 barb; the free half of the barbule is much narrower, and 

 fines away to a mere filament. Where this thinning com- 

 mences it is seen that the flange presents a broken appearance, 

 there being three indentations giving a short " dog-tooth " 

 edge (fig. 2, 2) ; beyond that the flange fines away. If a 

 single barb be examined, the proximal barbules appear 

 coming off at regular intervals, and at their proximal end 

 appear to join on to an edge-piece running parallel to the 

 barb. If now they are torn asunder with needles, this edge 

 is seen to be formed by the attenuated halves of these barbules 

 overlapping one another and being turned at a considerable 

 angle upon the other half. The '' dog-tooth ^^ portion allows 

 of this folding in the flange without any crumpling (fig. 3, 

 a and /3) . This arrangement gives strength and elasticity to 



