ranges from the equator to northern Asia as far as the river
Amur, and to the isothermal of 32 deg. Fahr. The mountain
sparrow (Fasser montana) is abundant in Java and
Singapore in a uniform equatorial climate, and also inhabits
Britain and a considerable portion of northern Europe.
It is true that most terrestrial animals are restricted to
countries not possessing a great range of temperature or
very diversified climates, but there is reason to believe
that this is due to quite a different set of causes, such
as the presence of enemies or deficiency of appropriate
food. When suppllad with food and partially protected from
enemies, they often show a wonderful capacity of enduring
climates very different from that in which they originally
flourished. Thus, the horse and the domestic fowl, both
natives of very warm countries, flourish without special
protection in almost every inhabited portion of the
globe. The parrot tribe form one of the most pre-eminently
tropical groups of birds, only a few species extending into
the warmer temperate regions; yet even the most exclusively
tropical genera are by no means delicate birds as regards
climate. In the Annals and Magazine of Natural History
for 1868 (p. 381) is a most interesting account, by Charles
Buxton, of the naturalization of parrots at Northrops Hall,
Norfolk. A considerable number of African and Amazonian
parrots, Bengal parroquets, four species of white and rose
crested cockatoos, and two species of crimson lories, remained
at large for many years. Several of these birds bred, and
they almost all lived in the woods the whole year through,
refusing to take shelter in a house constructed for their
use. Even when the thermometer fell 6 deg. below zero, all
appeared in good spirits and vigorous health. Some of these
birds have lived thus exposed for many years, enduring the
English cold easterly winds, rain, hail and snow, all through
the winter--a marvellous contrast to the equable equatorial
temperature (hardly ever less than 70 deg. ) to which many of
them had been accustomed for the first year or years of their
existence. Similarly the recent experience of zoological
gardens, particularly in the case of parrots and monkeys, shows
that, excluding draughts, exposure to changes of temperature
without artificial heat is markedly beneficial as compared
with the older method of strict protection from cold.
Hardly any group of Mammalia is more exclusively tropical
than the Quadrumana, yet, if other conditions are favourable,
some of them can withstand a considerable degree of cold.
Semnopithecus schistaceus was found by Captain Hutton at an
elevation of 11,000 feet in the Himalayas, leaping actively
among fir-trees whose branches were laden with snow-wreaths.
In Abyssinia a troop of dog-faced baboons was observed by W. T.
Blanford at 9000 feet above the sea. We may therefore conclude
that the restriction of the monkey tribe to warm latitudes is
probably determined by other causes than temperature alone.
Similar indications are given by the fact of closely allied
species inhabiting very extreme climates. The recently extinct
Siberian mammoth and woolly rhinoceros were closely allied to
species now inhabiting tropical regions exclusively. Wolves
and foxes are found alike in the coldest and hottest parts
of the earth, as are closely allied species of falcons, owls,
sparrows and numerous genera of waders and aquatic birds.
A consideration of these and many analogous facts might induce
us to suppose that, among the higher animals at least, there
is little constitutional adaptation to climate, and that in
their case acclimatization is not required. But there are
numerous examples of domestic animals which show that such
adaptation does exist in other cases. The yak of Thibet cannot
long survive in the plains of India, or even on the hills
below a certain altitude; and that this is due to climate,
and not to the increased density of the atmosphere, is shown
by the fact that the same animal appears to thrive well in
Europe, and even breeds there readily. The Newfoundland
dog will not live in India, and the Spanish breed of fowls
in this country suffer more from frost than most others.
When we get lower in the scale the adaptation is often more
marked. Snakes, which are so abundant in warm countries,
diminish rapidly as we go north, and wholly cease at lat.
62 deg. . Most insects are also very susceptible to cold, and
seem to be adapted to very narrow limits of temperature.
From the foregoing facts and observations we may conclude,
firstly, that some plants and many animals are not
constitutionally adapted to the climate of their native country
only, but are capable of enduring and flourishing under
a more or less extensive range of temperature and other
climatic conditions; and, secondly, that most plants and
some animals are, more or less closely, adapted to climates
similar to those of their native habitats. In order to
domesticate or naturalize the former class in countries not
extremely differing from that from which the species was
brought, it will not be necessary to acclimatize, in the
strict sense of the word. In the case of the latter class,
however, acclimatization is a necessary preliminary to
naturalization, and in many cases to useful domestication,
and we have therefore to inquire whether it is possible.
Acclimatization by Individual Adaptation.---It is evident
that acclimatization may occur (if it occurs at all) in two
ways, either by modifying the constitution of the individual
submitted to the new conditions, or by the production of
offspring which may be better adapted to those conditions
than their parents. The alteration of the constitution
of individuals in this direction is not easy to detect,
and its possibility has been denied by many writers. C.
Darwin believed, however, that there were indications that
it occasionally occurred in plants, where it can be best
observed, owing to the circumstance that so many plants are
propagated by cuttings or buds, which really continue the
existence of the same individual almost indefinitely. He
adduced the example of vines taken to the West Indies from
Madeira, which have been found to succeed better than those
taken directly from France. But in most cases habit, however
prolonged, appears to have little effect on the constitution of
the individual, and the fact has no doubt led to the opinion
that acclimatization is impossible. There is indeed little
or no evidence to show that any animal to which a new climate
is at first prejudicial can be so acclimatized by habit that,
after subjection to it for a few or many seasons, it may
live as healthily and with as little care as in its native
country; yet we may, on general principles, believe that under
proper conditions such an acclimatization would take place.
Acclimatization by Variation.---A mass of evidence exists
showing that variations of every conceivable kind occur
among the offspring of all plants and animals, and that,
in particular, constitutional variations are by no means
uncommon. Among cultivated plants, for example, hardier and
more tender varieties often arise. The following cases are
given by C. Darwin:-Among the numerous fruit-trees raised
in North America some are well adapted to the climate of the
northern States and Canada, while others only succeed well
in the southern States. Adaptation of this kind is sometimes
very close, so that, for example, few English varieties of
wheat will thrive in Scotland. Seed-wheat from India produced
a miserable crop when planted by the Rev. M. J. Berkeley
on land which would have produced a good crop of English
wheat. Conversely, French wheat taken to the West Indies
produced only barren spikes, while native wheat by its side
yielded an enormous harvest. Tobacco in Sweden, raised
from home-grown seed, ripens its seeds a month earlier
than plants grown from foreign seed. In Italy, as long as
orange trees were propagated by grafts, they were tender;
but after many of the trees were destroyed by the severe
frosts of 1709 and 1763, plants were raised from seed, and
these were found to be hardier and more productive than the
former kinds. Where plants are raised from seed in large
quantities, varieties always occur differing in constitution,
as well as others differing in form or colour; but the
former cannot be perceived by us unless marked out by their
behaviour under exceptional conditions, as in the following
cases. After the severe winter of 1860-1861 if was observed
that in a large bed of araucarias some plants stood quite
unhurt among numbers killed around them. In C. Darwin's
garden two rows of scarlet runners were entirely killed by
frost, except three plants, which had not even the tips of
their leaves browned. A very excellent example is to be
found in Chinese history, according to E. R. Huc, who, in his
L' Empire chinois (tom. ii. p. 359), gives the following
extract from the Memoirs of the Emperor Khang:---``On the
1st day of the 6th moon I was walking in some fields where
rice had been sown to be ready for the harvest in the 9th
moon. I observed by chance a stalk of rice which was already in
ear. It was higher than all the rest, and was ripe enough
to be gathered. I ordered it to be brought to me. The grain
was very fine and well grown, which gave me the idea to
keep it for a trial, and see if the following year it would
preserve its precocity. It did so. All the stalks which came
from it showed ear before the usual time, and were ripe in
the 6th moon. Each year has multiplied the produce of the
preceding, and for thirty years it is this rice which has
been served at my table. The grain is elongate and of a
reddish colour, but it has a sweet smell and very pleasant
taste. It is called Vu-mi, Imperial rice, because it was
first cultivated in my gardens. It is the only sort which
can ripen north of the great wall, where the winter ends
late and begins very early; but in the southern provinces,
where the climate is milder and the land more fertile, two
harvests a year may be easily obtained, and it is for me
a sweet reflection to have procured this advantage for my
people.'' Huc adds his testimony that this kind of rice
flourishes in Manchuria, where no other will grow. We
have here, therefore, a perfect example of acclimatization
by means of a spontaneous constitutional variation.
That this kind of adaptation may be carried on step by step to
more and more extreme climates is illustrated by the following
examples. Sweet-peas raised in Calcutta from seed imported
from England rarely blossom, and never yield seed; plants
from French seed flower better, but are still sterile;
but those raised from Darjeeling seed (originally imported
from England) both flower and seed profusely. The peach
is believed to have been tender, and to have ripened its
fruit with difficulty, when first introduced into Greece;
so that (as Darwin observes) in travelling northward during
two thousand years it must have become much hardier. Sir J.
Hooker ascertained the average vertical range of flowering
plants in the Himalayas to be 4000 ft., while in some cases
if extended to 8000 ft. The same species can thus endure a
great difference of temperature; but the important fact is,
that the individuals have become acclimatized to the altitude
at which they grow, so that seeds gathered near the upper
limit of the range of a species will be more hardy than those
gathered near the lower limit. This was proved by Hooker
to be the case with Himalayan conifers and rhododendrons,
