INTRODUCTION. xi

But the variation does not end here; for in such species as possess freckled coverts, the
freckles become finer as the bird becomes older; and in those in which the coverts are
black, the black becomes purer and more dense. In the case of Pharomacrus mocinno
the young males in their first plumage are only distinguishable from the females by their
more pointed rectrices; but after they assume the normal colour of the adult bird, the
longer they live the longer and wider the tail-coverts become, the more prolonged the

wing-coverts, and the more elevated the crest.

In the ‘Comptes Rendus’ for 1857 (vol. xlv. p. 688), Professor Bogdanoff gave an
account of some chemical experiments which he made with the plumes of Pharomacrus
auriceps, and showed that by immersing the red breast-plumes in spirit all the colour
is taken out of them. The red pigment of these feathers he calls “zooxanthine.” We
remember that M. Jules Verreaux has also stated that in heavy storms of rain, the red
breast of Hapaloderma narina at the Cape becomes completely washed out, and is renewed
again in its full intensity only after an interval of some days. A similar fact is noticed

in the red wing-feathers of the Touracous and in some of the American Chatterers (Cotinga).

In the fourth part of the ‘Museum Heineanum, Messrs. Cabanis and Heine introduce
a number of new generic names into this family of birds. The value of these genera
is very small. Thus we find Pothinus used for a group of yellow-breasted Trogons including
T. aurantiventris, a species perhaps not properly separable from 7. puella, which is left
in true Trogon. The rest of the yellow-breasted Trogons are placed in a genus Aganus ;
whilst for 7. swrweura another generic name, Hapalophorus, is proposed, the species being
in fact most nearly allied to 7. aurantius. For the black-tailed Trogons the generic name
Troctes is proposed, and with more reason than in the other instances; but here a sub-
division seems hardly admissible, seeing that an intermediate species exists in 7’. clathratus,
which partly closes the gap between Trogon and Troctes. Lastly, the genus Pharomacrus
is divided into two, Tanypeplus and Pharomacrus ; but this, again, seems to me to be carrying

generic subdivision too far.

The species described as Trogon neowenus and placed, in the first part of this edition

of the ‘'Trogonidee,’ under the new generic name LHuptilotis, is also considered by Messrs.

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