C PTERYLOGRAPHY. 



are attached below to the base of the tube, and above to the pith of the stem. The parenchy- 

 niatous portion of the stem is called, in opposition to the tube,, the SHAFT (rltacJiis, Schaft), and 

 it is from the flattened sides of this that the barbs issue. On its entire outer surface the shaft 

 acquires a horny coat, evidently a continuation of the tube, the arched surface of which it 

 retains on the outer side, whilst the posterior side of the shaft, which is turned towards the body 



merely by the name of the follicle) passes beyond the limit of the cutaneous pouch in which it 

 is inserted, is its opening at the superior extremity. As soon as this has occurred, the apex of the 

 feather issues from the opening in the form of a pencil of fine rays, and spreads out into a tuft at the 

 end (Plate I, fig. 10). As the pencil rises it becomes larger and stronger, the opening becomes wider, 

 nnd the follicle is then seen open in its whole width. Still the feather exhibits no change; it 

 is exactly like a pencil, and roundish and cylindrical throughout. But as it grows larger, a somewhat 

 stronger branch makes its appearance beneath the others, which are all of equal size, on the anterior 

 surface, and on that side which, of all parts of the feather, is most averted from the body. This 

 stronger branch is the upper extremity of the stem, and it is easily seen that the other branches which 

 are next to it on each side, do not descend parallel to it into the follicle, but are attached to it, and are 

 therefore to be regarded as its branches. I find, however, at least in the feathers of the trunk, that in 

 the first place two branches of equal size always unite in a fork, and form the commencement of the 

 stem, and that then the two following lateral branches meet the stem of the first fork at the same 

 height. The same structure is also exhibited in the filoplumes (Plate I, figs. 7 and 8), but with this 

 difference, that only a few branches occur at the extremity of the shaft. Just as in these feathers (see 

 further on) the uppermost part of every feather is perfectly destitute of pith, clear and transparent ; and 

 it is only lower down, beyond the fourth or fifth pair of branches, that it becomes more opaque 

 and parenchymatous. If we trace the course of the stem further, we find that it penetrates, with the 

 finer branches lying close to it, into the follicle, and loses itself with them in the granular layer within 

 the follicle upon the surface of the matrix. This granular layer, which I shall call feather-material, 

 forms a complete cylinder, coating the matrix on all sides, and emitting the already-formed extremities 

 of the branches from its superior free margin. This cylindrical primitive form, which is consequently 

 possessed by all young feathers, is easily recognised even in the fully-developed feather. It is very 

 distinctly shown in the tube up to the point where it passes into the shaft. This point is characterised 

 by the umbiliciform pit described by Nitzsch ; and this pit is properly nothing but the superior orifice of 

 the tube, narrowed by the inferior end of the thick shaft. The correctness of this view is still more 

 distinctly seen in feathers with a large aftershaft, but most clearly in those of the Cassowary, in which 

 both shafts are of equal size. The shaft of the feather is to a certain extent a prolongation, combined 

 with thickening, of the upper margin of the tube at its outermost point, and the aftershaft a second 

 prolongation of the same kind, at the innermost and precisely opposite point. Even in the remiges, 

 which never have an aftershaft, the original cylindrical arrangement is still recognisable in the fact, 

 that the whole of their barbs form a closed curve, an ellipse, which descends on both sides of the shaft, 

 and passes below round the umbiliciform pit, so that, in this way, both series of barbs are connected. 

 The figure of such a wing- feather (Plate I, fig. 18) shows, how both series of barbs (d and e) gradually 

 approach each other as they descend, and would run round the pit (placed just below a), if a portion 

 of the upper margin of the quill, with the small and almost down-like barbs, were not removed by the 

 incision which opens the tube. 



If we now trace the barbs as they descend to the base of the feather between the follicle and the 

 matrix (Plate I, fig. 11), it soon appears that they are at first still completely separate, and that their 

 two rows of barbules adhere closely to the sides of the barb. Further down these barbules merely 

 present oblique lines on the sides of the barbs, and at last completely disappear, so that from this point 



