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Show 448 MR. A. H. GARROD ON THE [May 15, down in the case of Euryleemus would have further confirmed Miiller in his views, and makes the question as to the ordinal importance of the Passerine group one of vital ornithological interest. M y subclass Anomalogonatse1 very closely corresponds with the Miillerian " Insessores," which comprises the Cuvierian order so termed, together with the Scansores. At the present time its importance would be considered supraordinal by all; and it is not customary now to divide that large division into three sections, 1. Oscines, 2. Tracheophonce, 3. Picarii, as was done, though not with any great feeling of certainty, by the able German biologist. W e include the Oscines and Tracheophonae, together with the "Ampelidse and Tyrannidse," in the order PASSERES. Why do we do so ? 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 biologists 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 fundamental characters happened to be can be only made at the present time (as far as soft parts are concerned, at least) by a correlation of the non-varying details. No Passerine bird being otherwise, they probably had (1) the hallux alone of all the toes directed backwards, (2) short, simple colic cseca, (3) a nude oil-gland, together with the special pterylosis of the group, (4) only one carotid artery, the left, (5) a sternum with a single notch on each side of the carina, together with a bifurcate manubrium, (6) a truncated vomer with the anterior angles of which the nasal cartilages joined, (7) a peculiar insertion to the tensor patagii brevis muscle of the wing. As in all but the Eurylaimidae, the deep flexor tendon of the hallux is free from that to the other digits of the foot, at the same time that the Eurylaimidse agree with by far the majority of the class Aves in this respect (whilst in the characterizing features above stated they are completely Passerine), it is evident that the ancestral type which forms the basis of our definition, lived at a period prior to the loss of the vinculum between the pedal deep flexor tendons, because the probability that the vinculum may have reappeared in them in a condition identical with that in other birds is infinitely small. This view is confirmed by the nature of the syrinx, as far as we are acquainted with it, J. Miiller not having been able to detect any intrinsic muscles in Corydon sumatranus2, the only species he had the 1 P. Z. S. 1874, p. 111. *• Loc. cit. p. 32. |