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.