448 MR. A. H. GARROD ON THE [May 15, 



down in the case of Euryloemus would have further confirmed 

 Miiller in his views, and makes the question as to the ordinal im- 

 portance of the Passerine group one of vital ornithological interest. 



My subclass Anomalogonatse' very closely corresponds with the 

 Miill'erian " 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. Tracheophonee, 3. Picarii, as was done, though not 

 with any great feeling of certainty, by the able German biologist. 

 We include the Oscines and Tracheophonse, together with the 

 " Ampehdae 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 classi- 

 fication 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 caeca, (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 trun- 

 cated 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 Eurylaimidse, 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 ac- 

 quainted with it, J. Miiller not having been able to detect any in- 

 trinsic muscles in Corydon sumatranus '', the only species he had the 

 ' P.Z.S. 1874, p. 111. » Loc. cit. p. 32. 



