art of the specific character; they
exhibit the same phenomena, again and again, and indicate certain fixed
and invariable relations between the physiological peculiarities of the
plant, and the influence of certain external agents. They afford no
ground for questioning the instability of species, but rather the
contrary; they present us with a class of phenomena, which, when they
are more thoroughly understood, may afford some of the best tests for
identifying species, and proving that the attributes originally
conferred endure so long as any issue of the original stock remains upon
the earth.

CHAPTER XXXV.

WHETHER SPECIES HAVE A REAL EXISTENCE IN NATURE--_continued_.

Limits of the variability of species--Species susceptible of
modification may be altered greatly in a short time, and in a few
generations; after which they remain stationary--The animals now
subject to man had originally an aptitude to domesticity--Acquired
peculiarities which become hereditary have a close connexion with
the habits or instincts of the species in a wild state--Some
qualities in certain animals have been conferred with a view of
their relation to man--Wild elephant domesticated in a few years,
but its faculties incapable of further development.

_Variability of a species compared to that of an individual._--I
endeavored, in the last chapter, to show, that a belief in the reality
of species is not inconsistent with the idea of a considerable degree of
variability in the specific character. This opinion, indeed, is little
more than an extension of the idea which we must entertain of the
identity of an individual, throughout the changes which it is capable of
undergoing.

If a quadruped, inhabiting a cold northern latitude, and covered with a
warm coat of hair or wool, be transported to a southern climate, it will
often, in the course of a few years, shed a considerable portion of its
coat, which it gradually recovers on being again restored to its native
country. Even there the same changes are, perhaps, superinduced to a
certain extent by the return of winter and summer. We know that the
Alpine hare (_Lepus variabilis_, Pal.) and the ermine, or stoat,
(_Mustela erminea_, Linn.) become white during winter, and again obtain
their full color during the warmer season; that the plumage of the
ptarmigan undergoes a like metamorphosis in color and quantity, and that
the change is equally tempor