ADAPTATION TO SUEROUNDINGS. 
13 
member of the Plover family (Charadriidce). In the upper 
division of the case are shown the eggs, newly-hatched young, 
and young males and females in the first autumn plumage ; 
as well as old males and females in winter, when both 
sexes are exactly alike in colour, size alone distinguishing 
them. The large group occupying the lower part of this case 
consists of adult birds in the plumage they assume in the breed- 
ing time (May and June). In the female the only alteration 
from the winter state is a darker and richer colouring, but in 
the males there is a special growth of elongated feathers about 
the head and neck, constituting the " ruff," from which the bird 
derives its name. In addition to this peculiarity, another, 
rare among animals in a wild state (though common among 
domesticated breeds), may be observed, that of striking diversity 
of colour in different individuals. Of the twenty-three specimens 
shown in the case no two are entirely alike. 
Next in order stands a case displaying the remarkable Group of Wild 
variations, according to season and age, in the plumage of the frating^Sea- 
Wild Duck, or Mallard {Anas hoscas). The most noticeable sonal Change 
feature in the plumage-changes of this group of birds is the °^ ^^^^^S^- 
assumption in summer by the males of certain species of an 
" eclipse-plumage," closely resembling the one worn by the 
females at all seasons. At other times the males are much 
more brilliantly coloured than their partners. The eclipse- 
plumage corresponds to the winter, or non-breeding dress of 
other birds which have a seasonal change. 
On the same side of the hall follow two cases illustrating Cases iUus- 
the adaptation of the colour of animals to their natural sur- V^^^^^,- 
^ ^ Adaptation of 
roundmgs, by means of which they are rendered less con- Colour to 
spicuous to their enemies or their prey. The first contains a conditions ^ 
specimen of a Mountain or Variable Hare (the common species 
of the north of Europe), a Stoat, and a Weasel, and some 
Willow- Grouse and Ptarmigan, as well as an Arctic Pox, 
in their summer dress, all obtained in Norway, showing the 
general harmony of their colouring at this season to that of 
the rocks and plants among which they live. The second case 
shows examples of the same animals obtained from the same 
country in winter, when the ground was covered with snow. 
Such striking changes as these only occur in latitudes and 
