ON THE ANATOMY OF PASSERINE BIRDS. 369 
Eurylemine. Such being the case, either Sundevall’s character no 
longer holds, or the Eurylemide are not Passeres. 
In his invaluable memoir on the voice-organs of Passerine birds,* a 
translation of which, by my friend Mr. F. J. Bell, wiil shortly be pub- 
lished at Oxford (by the Clarendon Press), J. Miller was so overcome 
by the flood of facts which he had discovered, that he remarks “It is, 
then, now thoroughly proved that the singing birds cannot be separated, 
as an order, from the rest of the Passeres (of Cuvier). There is only 
a large division of Insessores or Passerines which must also include the 
Scansores. This order of Insessores will contain birds with the most 
varied supply of vocal muscles, as well as birds which do not possess 
these muscles, every intermediate condition being found.” The fact 
that an important generalization, such as that of Sundevall above con- 
sidered, breaks down in the case of Hurylemus would have further Page 443. 
_ confirmed Miiller in his views, and makes the question as to the ordi- 
nal importance of the Passerine group one of vital ornithological 
interest. 
My subclass Anomalogonatet very closely corresponds with the 
Miillerian “Insessores,” which comprises the Cuvierian order so 
termed, together with the Scansores. At the present time its import- 
ance would be considered supraordinal by all; and it is not customary 
now to divide that large division inte three sections, 1. Oscines, 
‘2. Tracheophone, 3. Picarii, as was done, though not with any great 
_ feeling of certainty, by the able German biologist. We include the 
Oscines and Tracheophone, together with the “Ampelide and 
Tyrannide,” in the order PasszrEs. Why do we doso? For many 
reasons. 
_ First, because, since the promulgation of the theory of natural 
selection by Mr. Darwin, the doctrine of evolution has obtained a hold 
upon biologists. This doctrine makes us look upon the classification 
of animals and plants in a different aspect to that in which the biolo- 
gists of thirty years ago and more were wont to do. We do not 
expect to find all intermediate links between any two allied forms of 
life. Groups have become differentiated from their parent stocks, and 
when once independent have gone on developing in their special lines, 
without admixture with any other types. When the ancestral Passeres 
were first developed they possessed the potentiality for the production 
of all the peculiarities of their offspring; and the peculiarities which 
made them Passerine must form the fundamental basis for a definition 
of the group. The determination of what these fandamental charac- 
ters happened to be can be only made at the present time (as far as 
* “ Abh. k. Akademie d. Wiss. zu Berlin,” 1847. 
t “ Proceedings of the Zoological Society,” 1874, p. 111. (Supra, p. 208.) 
2B 
