INTEODrCTOEY COLLECTIOX. 
25 
environment, 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 examples in the upper part of the case, of 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 butterfly {Kcdlima 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 an- 
other living animal, belonging to a different species, family, or 
even order. The resemblamce in these cases 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 appear- 
ances can only be regarded at present as conjectural. AATiatever 
be the real explanation, the facts shown by the specimens in this 
case are very curious, and well worthy of careful consideration. 
Thenextcase contains a series of speciniens illustrating aZkVzzs??!., Group ilius- 
a condition in which the pigment or colouring matter, usually ^^^^^^ 
present in the tissues constituting the external covering of the 
body, and which gives them their characteristic hue, is absent. 
Individuals in this condition occur among many animals of 
various kinds, and are called " alhinos!' In some of the speci- 
mens shown in the case the albinism is complete, but in many 
it is partial, the absence of colouring matter being limited to 
portions of the surface only. 
A seventh case shows examples of the opposite condition. Group illus- 
called melanism, depending upon an excess of dark-coloured Mel^sm. 
pigment in the skin and its appendages, the hair, feathers, etc., 
beyond what is normally met with in the species. This is by 
no means so frequent as albinism. A black Leopard in the 
middle of the case is a good illustration. It is not a distinct 
species, but an individual variety of the common Leopard, born 
from parents of the normal colour. A black Bullfinch is intro- 
duced as an example of acquired melanism, the bird having 
turned black in captivity. Group illus- 
The last group shows that two forms of Crows wliich appear ^gj^f^^^^®^ 
quite distinct, and which, judged by their external characters. Forms in 
Nature. 
