494 MR. J. S. HUXLEY,ON THE 
from the sides they can scarcely be seen, as they are’ end-on to 
the eyes. When erected vertically, they seem, when viewed from 
the side, to be sticking straight upwards ; but when they are 
seen from in front, it is found that they diverge from each other 
at a considerable angle (Pls. I. & II. figs. 4, 5, 11). Durmeg 
erection, the individual feathers always diverge fanwise very 
considerably. Thus there are four conditions of the ear-tufts 
to be distinguished. 
They may be:—(a) Depressed. 
(1) Shut tight. 
(2) At rest (relaxed). 
(b) Hrected. 
(3) Vertically. 
(4) Laterally. 
The ruff is more complex in its attitudes, as im its structure. 
During depression it, too, may be either shut tight or lying easy. 
When really shut, it bears from the side a curious resemblance to 
the gill-covers of some eel-like fish : its rounded hinder border lies 
along the side of the cylindrical neck, whose outlines its own 
scarcely overlap, either dorsally or ventrally (fig. 1). When re- 
laxed (at rest), this resemblance disappears, for the feathers all 
diverge slightly, and the smooth appearance of the surface is 
lost. 
When the ruff is erected, the feathers composing it may be 
made to diverge in a single plane only, the original (longitudinal- 
vertical) plane of the “ gill-cover,” or they may diverge outwards 
as well, making an angle with the side of the head (movement in 
the transverse, as well as the sagittal plane). I do not think that 
they are ever moved in the transverse plane alone. Asa result 
of these movements, three chief forms can be taken on by the 
ruff. First there is the curtain form, m which motion in the 
vertical plane alone takes place, the ventral edge being brought 
forward till it makes an acute angle with the line of the chm 
(fig. 3), the two halves thus hanging like curtains on either side 
of the head. Then there is the pear-shaped condition (figs. 4, 
11), where there is a consideyable amount of forward and a 
moderate amount of transverse motion. The ruff in this state 
has its vertical height greater than its breadth (fig. 5). Owing 
to the transverse bristling of the feathers, the two halves of the 
vuff almost blend into a single whole; they can scarcely be 
distinguished either from the front or, stall less, from behind, 
whereas in the curtain form they are very distinct. Finally, 
there is the elliptical form, when, added to the same amount of 
Jongitudinal motion, the greatest possible amount of transverse 
bristling has taken place. The ruff is now actually broader than 
it is high (fig. 9), and the blending of the two halves is practically 
complete. There are, of course, intermediate states. Instead 
of “full pear-shaped,” you may have ‘half pear-shaped ” ; 
Ly | ; and 
between pear-shaped and elliptical there comes the circular. 
