14 
CENTRAL HALL. 
Case illustrat- 
ing Protective 
Resemblance 
of Desert 
Animals to 
their Sur- 
roundings. 
Mimicry. 
localities where the differences between the general external 
conditions in the different seasons are extreme, where the snow 
disappears in summer and remains on the ground during most 
of the winter. Even some of the species here shown do not 
habitually turn white in the less severe winters of their southern 
range, as the Stoat in England and the Hare in Ireland. In a 
few permanent inhabitants of still more northern regions, where 
the snow remains throughout the year, as the Polar Bear, 
Alaskan Bighorn Sheep, Greenland Ealcon, and Snowy Owl, 
the white coat is retained throughout the year. The white- 
ness of these animals must not be confounded with albinism 
(whiteness occurring accidentally in individuals normally of 
a different colour), illustrated in a case on the other side of 
the hall. 
The case on the east side of the hall nearest the great 
staircase contains examples of conformity of general style of 
colouring to surrounding conditions, as exemplified by some of 
the commoner birds, mammals, and reptiles of the Egyptian 
desert, placed on the stones and sand amid which they habitually 
dwell. The advantage of this colouring in concealing the her- 
bivorous species from their enemies, and enabling the carnivorous 
to approach their prey unperceived, is obvious. Many excellent 
cases of concealment by adaptation to surroundings, especially 
in eggs and young birds, may be seen among the groups in the 
bird gallery. 
More special modifications for the same purpose are shown in 
the adjacent bay on the east side of the hall by insects which 
closely resemble the objects, such as leaves, twigs, etc., 
among which they dwell. The close imitation of a dead leaf, 
presented by the Leaf-Butterfly (Callima inachis), when its wings 
are closed, could not be surpassed. A further stage of the same 
condition, called " Mimicry," is where the object resembled, or 
mimicked, is another living animal, belonging to a different 
species, family, or even order. The resemblance in these instances 
is also believed to be for protection, or to be in some way 
advantageous to the animal possessing it. We know, however, 
so little of the habits and life-history of animals in a state of 
nature that many of the purposes supposed to be served by 
particular colours or appearances can only be regarded at 
