12 
CENTRAL HALL, 
Case illustrat- 
ing Protective 
Besemblance 
of Desert 
Animals to 
their Sur- 
roundings. 
few permanent inhabitants of still more northern regions, where 
the snow remains throughout the year, as the Polar Bear, 
Greenland Falcon, and Snowy Owl (of which a specimen is 
shown on the wing in the upper part of the winter case), the 
white colour is retained throughout the year. The whiteness 
of these animals must not be confounded with alhinism 
(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 environment, especially 
in eggs and young birds, may be seen among the groups in the 
bird gallery. 
Mimicry. 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 inanimate objects, as leaves, twigs, &c., 
among which they dwell. The close imitation of a dead leaf, 
presented by the Leaf-Butterfly (Callima inachis), when its v/ings 
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 
present as conjectural. Whatever be the real explanation, the 
facts shown by the specimens in this bay are very curious, and 
worthy of careful consideration. 
Group iiius- xhe next case on the east side of the middle of the hall 
Aib^^xn. contains a series of specimens illustrating alhinism, a condition 
