PHYLOGENY OF THE PALZOGNATHA AND NEOGNATHZ., 165 
The Structure and Homologies of' the Adult and Nestling 
Remiges of Casuarius. 
The Nestling—The youngest nestling in which these can be studied is that of a 
stuffed C. casuarius salvadorii (Rothschild Mus.). 
In the dried wing of this there are 6 remiges. These are widely spaced, and 
seated in a distinct posterior wing-membrane as in Neognathe. Each consists of a 
moderately long calamus and a long and tapering rhachis bearing from 4-5 pairs of 
symmetrically disposed rami set very far apart. There is but the feeblest trace of the 
fusion between the prepenna and the displacing definitive feather now under discussion. 
In C. casuarius sclateri the growth of the wing-spines has proceeded a stage farther. 
The definitive feather is seen to bear rami as well as prepenne. 
In Casuarius lorie the quill-spines have grown very long and have lost the prepenna. 
The 5th or innermost spine, representing the 3rd cubital remex, yet bears a few rami. 
In this stage, and in the last described (C. ¢. sclateri), we get an inkling into the 
developmental history of these remarkable wing-spines. 
This is not the place for a recapitulation of the developmental history of a feather, 
yet it would be well to recall one or two facts concerned with this for the better under- 
standing of what is to follow. 
The axis of a feather, then, is divisible into two parts—the calamus or quill, and the 
rhachis or shaft. ‘The latter appears to be a continuation forwards of the dorsal region 
of the tubular calamus. This being so, it is obvious that this drawn-out portion must 
have two lateral free edges. These in the normal feather turn inwards towards the 
middle line and finally meet, leaving a very fine seam to indicate the line of junction. 
But the calamus, it will be remembered, is a thin, dense, horny, and semitransparent 
structure and perfectly hollow, whilst the rhachis in section is solid, being composed of 
an outer layer continuous with that of the calamus, and an inner, medullary portion or 
pith—a white, soft, cellular structure resembling elder-pith. This pith seems to be 
added for the sake of supporting the outer horny membrane, thus insuring lightness, 
toughness, and strength. The whole forms the shaft. 
The dorsal elongated region of the shaft, now swollen out by pith, forms a sort of 
plug to the otherwise open mouth of the calamus. The ventral edge of this mouth is 
always visible. It forms the boundary of the upper umbilicus. 
The aftershaft, so conspicuous a feature in the feathers of the Cassowaries, represents 
an elongation of the ventral region of the calamus exactly similar to that which obtains 
on the dorsal. ‘Thus we have a dorsal and ventral rhachis. 
In the remiges of C. loriw and C. ¢. sclateri we have only the dorsal rhachis, and 
this is of great interest as only its outer layer is present, there being no pith-cells. 
This layer takes the form of a delicate scroll-like, ribbon-shaped lamina whose free 
edges turn inwards, but from the absence of the packing material, or pith, they fail to 
meet in the middle line (Pl. XLV. fig. 14 a). 
vou. Xv.—Part v. No. 8.—December, 1900. 28 
