RESEMBLANCES AMONG ANIMALS. 123 
external form and colouring of animals is adapted to 
be useful to them, either by concealing them from their 
enemies or from the creatures they prey upon. It has, 
T hope, been shown that the subject is one of much 
interest, both as regard a true comprehension of the 
place each animal fills in the economy of nature, and 
the means by which it is enabled to maintain that. 
place; and also as teaching us how important a part 
is played by the minutest details in the structure 
of animals, and how complicated and delicate is the 
equilibrium of the organic world. 
My exposition of the subject having been necessarily 
somewhat lengthy and full of details, it will be as 
well to recapitulate its main points. 
There is a general harmony in nature between the 
colours of an animal and those of its habitation. 
Arctic animals are white, desert animals are sand- 
coloured ; dwellers among leaves and grass are green ; 
nocturnal animals are dusky. These colours are not 
universal, but are very general, and are seldom re- 
versed. Going on a little further, we find birds, 
reptiles, and insects, so tinted and mottled as exactly 
to match the rock, or bark, or leaf, or flower, they 
are accustomed to rest upon,—and thereby effec- 
tually concealed. Another step in advance, and we 
have insects which are formed as well as coloured so 
as exactly to resemble particular leaves, or sticks, or 
mossy twigs, or flowers; and in these cases very 
peculiar habits and instincts come into play to aid 
in the deception and render the concealment more 
