C. J. Sundevall on the. Wings of Birds. 399 



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 1 

 gi'owth 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- 

 warieSj in which the accessory plume is as large and of the 

 same structure as the outer shaft and vane. On the body of 

 Lagopus the accessory plume is |, 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 Nitzsch — 

 Strix, 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 



