The Avicultural Magazine.



Pollex



A STUDY IN PTERYLOSIS: NESTLING YUCATAN JAY,

EIGHTEEN DAYS OLD.


Contrary to popular belief, the bodies of birds are not, as a rule, uniformly feathered. In this

beautiful photograph the pterylosis, or arrangement of the feather-tracts, is well shown. We

readily distinguish, for example, a median ventral feather-tract, with a bare space or apterion

to either side. The pollex or thumb is recognisable tipped with its feather; then come the

primary, followed by the secondary, quids. On the shoulders are seen the scapular feather-

tracts, and there is a whorl of feathers about the external ear. — G. R.



Photo by Maurice Amsler. M.B.



Adlard & Son & West Newman, Ltd.



