cleared up, would be interesting; if, for
instance, it could be shown that the greyhound, bloodhound, terrier,
spaniel, and bull-dog, which we all know propagate their kind so truly,
were the {17} offspring of any single species, then such facts would have
great weight in making us doubt about the immutability of the many very
closely allied natural species--for instance, of the many foxes--inhabiting
different quarters of the world. I do not believe, as we shall presently
see, that the whole amount of difference between the several breeds of the
dog has been produced under domestication; I believe that some small part
of the difference is due to their being descended from distinct species. In
the case of some other domesticated species, there is presumptive, or even
strong evidence, that all the breeds have descended from a single wild
stock.

It has often been assumed that man has chosen for domestication animals and
plants having an extraordinary inherent tendency to vary, and likewise to
withstand diverse climates. I do not dispute that these capacities have
added largely to the value of most of our domesticated productions; but how
could a savage possibly know, when he first tamed an animal, whether it
would vary in succeeding generations, and whether it would endure other
climates? Has the little variability of the ass or guinea-fowl, or the
small power of endurance of warmth by the reindeer, or of cold by the
common camel, prevented their domestication? I cannot doubt that if other
animals and plants, equal in number to our domesticated productions, and
belonging to equally diverse classes and countries, were taken from a state
of nature, and could be made to breed for an equal number of generations
under domestication, they would vary on an average as largely as the parent
species of our existing domesticated productions have varied.

In the case of most of our anciently domesticated animals and plants, I do
not think it is possible to come to any definite conclusion, whether they
have descended from one or several wild species. The argument mainly relied
on by those who believe in the multiple origin {18} of our domestic animals
is, that we find in the most ancient records, more especially on the
monuments of Egypt, much diversity in the breeds; and that some of the
breeds closely resemble, perhaps are identical with, those still existing.
Even if this latter fact were found more strictly and generally true tha