399 
C. J. Sundevall on the Wings of Birds. 
quill-tube below the umbilicus like a little duplication. It 
has been regarded as an appendage, or as a small feather 
growing upon the larger one; but it should rather be re¬ 
garded from another point of view as being of exactly the 
same rank as the larger rhachis, although checked in its 
growth during development. According to this view there 
issue from each quill-tube two similar vane-bearing rhachides, 
and in point of fact we find the case to be so in the Casso¬ 
waries, in which the accessory plume is as large and of the 
same structure as the outer shaft and vane. On the body of 
Lag opus the accessory plume is f, and in Falco palumbarius 
half as long as the outer rhachis, but in both the vane is 
downy and not coherent. In all these cases we see distinctly 
that the umbilicus lies between the two rhachides, and that 
the latter are raised and furrowed on the opposite sides, so 
that the grooves of both terminate in the umbilicus, and are 
as it were a remaining trace of it. The obverse side of the 
accessory plume is thus turned towards the body; it is fur¬ 
nished with a sharply defined continuation of the quill-tube 
itself, just like the outer rhachis. The vane in both rhachides 
forms a single uninterrupted series, and in case the accessory 
plume is wanting, as in the quill-feathers, the vane follows 
the whole margin round the umbilicus, like a wreath. In 
the most highly developed feathers, the quill-feathers and 
the large covert-feathers, the accessory plume is always 
wanting, and in some birds it is deficient throughout the 
whole of their plumage. These are, according to Mtzsch— 
StricCj Linn., Pandion , Columba , and a great many of the 
Coccyges, Pterocles, Anas , Linn., and the Steganopodes. In 
the Song-birds, and in Aptenodytes , the accessory plume is 
quite small, downy, or rudimentary. The feathers of the last 
have the true shaft very thick. 
Second Chapter. 
Special Description of the different sorts of Wing-feathers. 
A. Quill-feathers (Pennse alares sive Remiges). 
These, as has already been stated, are distinguished from 
