Page:The Fauna of British India, including Ceylon and Burma (Birds Vol 1).djvu/46

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to each front toe. The Flexor longus hallucis arises from the outer condyle of the femur and from the intercondylar region. It accompanies, and is closely associated with, the Fl. profundus throughout its whole length. Passing also into the tendinous condition at the intertarsal joint, it crosses the Fl. profundus tendon near its middle, from behind and from without inwards to be inserted on the terminal phalanx of the hind toe. This, at least, is what obtains in all the Passeres save the Eurylœmidæ, where the hallucis tendon anchors itself to the profundus tendon at the point where the two tendons cross, by a number of tendinous fibres, to form what is known as a "vinculum." No less than eight different modes of anchorage between these two tendons are recognized. The typical Passeriform type is No. VII. of this series; that of the Eurylœmidæ is No. 1.

Nitzsch, in laying the foundations of the study of the pterylosis, opened up a field of great promise, which, so far, has only very partially been explored by systematists. The attempt to use the number of the remiges as a factor in the subdivision of the Passeres has only resulted in the formulation of a test which is based on error. Thus, in the previous edition of this work an attempt was made to form two Groups of Passeres, the one displaying 9, the other 10 primaries. This was unfortunate, since all the so-called "9-primaried" Passeres possess 10 remiges, while many of the so-called "10-primaried" Passeres possess 11 remiges. The error has arisen from a failure to distinguish vestigial quills and their coverts. In the "9-primaried" Passeres the 10th may be reduced to the vanishing point. Where the 10th primary is conspicuously long, as in the Corvidæ, the 11th will be found as a "remicle," 1 cm. or more in length. Bearing these facts in mind, there can be no objection, for the sake of convenience, to the continued use of the division into 9-primaried and 10-primaried wings, the remicle being in both cases a negligible quantity.

So far, unfortunately, Ornithologists have made no more use of pterylosis than this numbering of the wing and tail-feathers. A vast amount of work has yet to be done, in investigating the pterylosis of the trunk, for the sake of the evidence it will unquestionably furnish as to the relationship of forms whose affinities can at the present be no more than guessed at. The Paridæ, Ampelidæ, Oriolidæ afford cases in point. True, we cannot discover this evidence by a study of the pterylosis alone—the osteology and myology of these puzzles must also be taken into account—but we shall have made great strides when this pteryological work has been thoroughly done. It is to be hoped that those who use these volumes will endeavour to take up this much neglected work.

The juvenile or "nestling" plumage of the Passeres affords very valuable data to the systematist. In the last edition of this