AVES. 
61 
the same author in the same journal (J. f. O. 1855^ pp. 113-117 ; 
1856_, pp. 129-132 inter alia). Herr von Homeyer quotes, and 
agrees to, the following results — at which, from a consideration 
of principles formerly announced by him, Herr T. Holland has 
also arrived : — 
A bird can only change its plumage, 
" 1. By the groAvth of new feathers in place of the old shed 
ones. 
” 2. By the growilig-forth of entirely new feathers. 
3. By the loss of certain parts of the feather in a mechanical 
manner. 
4. By the chemical influence of light and the atmosphere 
on the pigment of the feathers (and possibly by the operation 
also of external colouring agents) . 
‘^5. By the union of two or more of these processes. 
NEOSSOLOGY.* 
Blasius, J. H. Zur Unterscheidung des Dunenkleides der 
llaubvogel. Journ. f. Orn., 1864, pp. 276-289. 
The author treats in considerable detail of the differences 
observable in the young of the Accipitres, wdien clad in down, 
grouping them for tliis purpose conveniently (but, of course, 
arbitrarily) according to characters drawn from the legs and 
feet — whether covered entirely or in part with feathers, with 
scales, or with reticulated skin. He remarks on the very dif- 
ferent colouring which the young of Buteo vulgaris present, 
even from the earliest age. There are (1) those with pure white 
down. These grow up into the pale examples with white under- 
surfaces, whose feathers never have a cross marking, and their 
under tail-coverts and bellies only a single shaft-streak, their 
breasts being thinly and their backs thickly spotted. (2) Those 
with uniform ashy -grey down, having constantly a pure white 
spot on the hind-head. From these originate the dark speci- 
mens which in mature plumage always have cross bars on the 
feathers of the underside, especially on the flanks and thighs. 
(3) Those with light whitish- grey bodies and pale, almost 
white, heads, with a Avhite longitudinal streak on the hind-head. 
These vary much in the intensity of their colouring, and when 
mature show a corresponding inconstancy, fluctuating between 
the two extremes. The paper contains remarks on most of the 
European species of Falconidce and several of the Strigidee. 
* The attention of many ornithologists having been of late more than ever 
turned to the study of birds at their very earliest age, we have thought it 
might be convenient for such persons to place together the notices of those 
publications which treat of this branch of study. This being the case, we 
trust the necessity of inventing a new term will be admitted. 
