CHARACTERS OF SPECIES.— LOCALITY. S85 
upon the most remote differences of locality. The 
Sphinx convolvuli and the Cynthia cardui—both well- 
known British insects —are likewise found in different 
parts of Asia, and even occur in New Holland. That 
pretty yellow butterfly, the ELurymus Electra of the 
south of Europe, and of Southern Africa, cannot be 
discriminated from those found in this country. 
(345.) Individuals of a species which show any de- 
viation from the usual characters by which that species 
is discriminated, are called varieties. These deviations 
from the ordinary characteristics of their race originate 
from a variety of causes; among which, climate, food, 
and domestication are the most influential. In nearly 
all cases, however, a variety is not permanent ; for, the 
local or influential causes being removed, the generation 
which succeeds assumes all the genuine lineaments of 
the race from whence it originally sprang. Animals, | 
whose chief metropolis is in a temperate climate, be- 
come smaller when they extend their limits into a 
warmer region, and vice versd. ‘The size of an animal 
is greatly influenced both by the quantity and quality 
of its food, no less than by its location ; and both these, 
again, affect its colour. Variation in the colour of 
quadrupeds, in a state of nature, is more rarely observed 
than in birds; although, in a domesticated state, the 
former seem most disposed to deviation from the natural 
standard. The ox, dog, and cat are familiar instances of 
this fact ; where the diversities of colour are much more 
remarkable than in the fowl, duck, goose, and turkey. 
Insects of the lepidopterous and the neuropterous or- 
ders are more prone to these variations from their 
original type, than any other. This is observable 
in the spots upon the wings of the Satyride, or Argus 
butterflies, and in the colours of the genus Agrion. The 
testaceous shellfish, however, are sometimes very incon- 
stant in their colours: strong instances of this are seen 
in many species of Helix, of Oliva, and of Tellina, as 
already intimated. 
(346.) The radiated animals are much more con- 
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