They certainly become adapted to
different climates under which they have long existed. It is notorious
that most of our best European breeds deteriorate in India.[69] The
Rev. R. Everest[70] believes that no one has succeeded in keeping the
Newfoundland dog long alive in India; so it is, according to
Lichtenstein,[71] even at the Cape of Good Hope. The Thibet mastiff
degenerates on the plains of India, and can live only on the
mountains.[72] Lloyd[73] asserts that our bloodhounds and bulldogs have
been tried, and cannot withstand the cold of the northern European
forests.

Seeing in how many characters the races of the dog differ from each other,
and remembering Cuvier's admission that their skulls differ more than do
those of the species of any natural genus, and bearing in mind how closely
the bones of wolves, jackals, foxes, and other Canidae agree, it is
remarkable that we meet with the statement, repeated over and over again,
that the races of the dog differ in no important characters. A highly
competent judge, Prof. Gervais,[74] admits, "si l'on prenait sans controle
les alterations dont chacun de ces organes est susceptible, on pourrait
croire qu'il y a entre les chiens domestiques des differences plus grandes
que celles qui separent ailleurs les especes, quelquefois meme les genres."
Some of the differences above enumerated are in one respect of
comparatively little value, for they are not characteristic of distinct
breeds: no one pretends that such is the case with the additional molar
teeth or with the number of mammae; the additional digit is generally
present with mastiffs, and some of the more important differences in the
skull and lower jaw are more or less characteristic of various breeds. But
we must not forget that the predominant power of selection has not been
applied in any of these cases; we have variability in important parts, but
the differences have not been fixed by selection. Man {37} cares for the
form and fleetness of his greyhounds, for the size of his mastiffs, for the
strength of the jaw in his bulldogs, &c.; but he cares nothing about the
number of their molar teeth or mammae or digits; nor do we know that
differences in these organs are correlated with, or owe their development
to, differences in other parts of the body about which man does care. Those
who have attended to the subject of selection will admit that, nature
having given variability, man,