448 C. J. Sundevall on the Whigs of Birds. 
colours also,, the external aspect of the hill and feet (hut 
certainly not their structure), their smaller size and resi¬ 
dence in trees, cause one to fancy that they are like the 
Song-birds, with which they have constantly been confounded. 
The case is different with Picus, for this genus appears to be 
a true transitional form, which, from its wing-structure, 
seems most to resemble the Song-birds; hut its want of the 
song-muscles, the structure of its feet, and the arrangement 
of the muscles of the wing, in combination with the above- 
mentioned character of the small outer coverts, determine 
most distinctly its place to he among the Cuckoo-like 
birds. 
We have here endeavoured to show that although there are 
manifold and considerable differences between the birds 
which are destitute of the song-apparatus, nevertheless they 
all possess a decided similarity of organization, owing to 
which they can and must be grouped together as a single 
great division of the class, in opposition to the Song-birds, 
which have another very distinct fundamental structure, but 
which present a very remarkable uniformity. This binary 
division is therefore the first natural division of the class of 
Birds ; the Song-birds must stand at one end of the series, and 
next to them come the Pici, Coccyges, &c. The other end is 
necessarily occupied by the Natatores. The Accipitres and 
Gallinse must retain their place in the middle of the series, 
which, however, certainly does not prevent our regarding 
them as the most highly developed, if we choose to 
do so. 
I have already developed these same views of the affini¬ 
ties and scientific arrangement of the forms of birds in my 
“ Ornithologiska System,” published in 1835 in the Kongl. 
Vet.-Ak. Handl. and they have only been strengthened by a 
continued investigation, although many alterations in the more 
special groupings have been rendered possible by an enlarged 
knowledge. 
In order to give a summary of the more important of these 
alterations the following Appendix is provided. 
