CHARACTERS OF SPECIES. ARE 
extended, permanent; and are therefore presumed to 
have had their origin when it came from the hands of 
its Creator.” Domestication and other causes will often 
produce some variation of these characters ; but, in a 
state of nature, such variations are seldom, if ever, 
perpetuated through many generations. Species are 
very generally considered the only distinct or definite 
divisions in nature. But, if this were correct, we should 
not have some naturalists calling that a species, which 
others contend is a variety. The theory of variation, 
again, by which natural assemblages are regulated, clearly 
proves that groups are more definite than species. 
(337.) It is difficult, if not impossible, to lay down 
any general rules for the positive discrimination of 
species ; but we may suggest to the student a few of 
those distinctions which are most absolute: these chiefly 
relate to form, sculpture, and colour. The form of an 
animal is as much distinctive of the group it belongs 
to, as of its specific character ; but so infinitely may the 
same general form be modified, either in the shape or 
the proportion of the whole, or of its parts, that, 
perhaps, the form, rigorously speaking, of no two 
species is the same. Under the general term of form, 
we comprehend size or bu/k, contour, or shape, and the 
proportion of the parts to each other. In regard to 
the first of these, the size of all animals will vary ac- 
cording to the scarcity or abundance, the richness or 
poorness, of their food: their. size will also be affected 
by their locality ; that is, by the temperature of the 
particular climate they have lived in, Animals which 
are found to be most abundant in cold or temperate 
regions, will, in proportion as they extend their range 
to others much warmer, become smaller than their 
brethren who had not quitted the central region as- 
signed to the species. The convolvulus sphinx of 
Europe, judging from the perfect insect, seems to be 
precisely the same in India as in Australia, in form, 
colour, and markings ; but the latter specimens are nearly 
one third less than the European examples ; thus showing 
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