trifling, we are led by the same train of thought to attribute each
slight variation much more to innate differences of constitution,
however caused, than to the definite action of the surrounding
conditions.

We are led to the same conclusion by considering the cases, formerly
alluded to, of fowls and pigeons, which have varied and will no doubt
go on varying in directly opposite ways, though kept during many
generations under nearly the same conditions. Some, for instance, are
born with their beaks, wings, tails, legs, &c., a little longer, and
others with these same parts a little shorter. By the long-continued
selection of such slight individual differences, which occur in birds
kept in the same aviary, widely different races could certainly be
formed; and long-continued selection, important as is the result, does
nothing but preserve the variations which appear to us to arise
spontaneously.

In these cases we see that domesticated animals vary in an indefinite
number of particulars, though treated as uniformly as is possible. On
the other hand, there are instances of animals and plants, which,
though exposed to very different conditions, both under nature and
domestication, have varied in nearly the same manner. Mr. Layard
informs me that he has observed amongst the Caffres of South Africa a
dog singularly like an arctic Esquimaux dog. Pigeons in India present
nearly the same wide diversities of colour as in Europe; and I have
seen chequered and simply barred pigeons, and pigeons with blue and
white loins, from Sierra Leone, Madeira, England, and India. New
varieties of flowers are continually raised in different parts of Great
Britain, but many of these are found by the judges at our exhibitions
to be almost identical with old varieties. A vast number of new
fruit-trees and culinary vegetables have been produced in North
America: these differ from European varieties in the same general
manner as the several varieties raised in Europe differ from each
other; and no one has ever pretended that the climate of America has
given to the many American varieties any general character by which
they can be recognised. Nevertheless, from the facts previously
advanced on the authority of Mr. Meehan with respect to American and
European forest-trees, it would be rash to affirm that varieti