Generally the term includes the unknown element of a
distinct act of creation. The term "variety" is almost equally difficult
to define; but here community of descent is almost universally implied,
though it can rarely be proved. We have also what are called
monstrosities; but they graduate into varieties. By a monstrosity I
presume is meant some considerable deviation of structure, generally
injurious, or not useful to the species. Some authors use the term
"variation" in a technical sense, as implying a modification directly due
to the physical conditions of life; and "variations" in this sense are
supposed not to be inherited; but who can say that the dwarfed condition of
shells in the brackish waters of the Baltic, or dwarfed plants on Alpine
summits, or the thicker fur of an animal from far northwards, would not in
some cases be inherited for at least a few generations? And in this case I
presume that the form would be called a variety.
It may be doubted whether sudden and considerable deviations of structure,
such as we occasionally see in our domestic productions, more especially
with plants, are ever permanently propagated in a state of nature. Almost
every part of every organic being is so beautifully related to its complex
conditions of life that it seems as improbable that any part should have
been suddenly produced perfect, as that a complex machine should have been
invented by man in a perfect state.
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