each man trying to keep the best dogs without
any thought of modifying the breed.

Even, without any change in the proportional
numbers of the animals on which our wolf
preyed, a cub might be born with an innate
tendency to pursue certain kinds of prey. Nor can
this be thought very improbable; for we often
observe great differences in the natural tendencies
of our domestic animals; one cat, for
instance, taking to catching rats, another mice;
one cat, according to Mr. St. John, bringing
home winged game, another hares, or rabbits,
and another hunting on marshy ground and
almost nightly catching woodcocks or snipes.
The tendency to catch rats rather than mice is
known to be inherited. Now, if any slight
innate change of habit or of structure benefited
an individual wolf, it would have the best chance
of surviving and of leaving offspring. Some of
its young would probably inherit the same habits
or structure, and by the repetition of this
process, a new variety might be formed which would
either supplant or coexist with the parent form
of wolf. Or, again, the wolves inhabiting a
mountainous district, and those frequenting the
lowlands, would naturally be forced to hunt
different prey; and from the continued
preservation of the individuals best fitted for the
two sites, two varieties might be slowly formed.
According to Mr. Pierce, there are two varieties
of the wolf inhabiting the Catskill Mountains
in the United States; one with a light
greyhound-like form, which pursues deer, and the
other more bulky, with shorter legs, which
more frequently attacks the shepherds' flocks.

The use and the disuse of particular organs
combine their effects with those of natural
selection, in the modification of species; use
strengthens and enlarges certain parts, and
disuse diminishes them. Such modifications are
inherited. Many animals have structures which
can be explained by the effects of disuse. As
Professor Owen has remarked, there is no greater
anomaly in nature than a bird that cannot fly;
yet there are several in this state. Since the
larger ground-feeding birds seldom take flight
except to escape danger, Mr. Darwin believes
that the nearly wingless condition of several
birds, which now inhabit or have lately inhabited
several oceanic islands, tenanted by.no beast of
prey, has been caused by disuse. The ostrich,
indeed, inhabits continents, and is exposed to
danger from which it cannot escape by flight;
but by kicking it can defend itself from its
enemies, as well as any of the smaller
quadrupeds. We may imagine that the early
progenitor of the ostrich had habits like those
of a bustard, and that as Natural Selection
increased in successive generations the size and
weight of its body, its legs were used more,
and its wings less, until they became incapable
of flight.

The eyes of moles and of some burrowing
rodents are rudimentary in size, and in some
cases are quite covered up by skin and fur.
This state of the eyes is probably due to gradual
reduction from disuse, but aided, perhaps, by
Natural Selection. In South America, a burrowing
rodent, the tuco-tuco, is even more
subterranean in its habits than the mole; and the
Spaniards, who often catch them, assert that they
are frequently blind. One, which Mr. Darwin
kept alive, was certainly in this condition, the
cause, as appeared on dissection, having been
inflammation of the nictitating membrane. As
frequent inflammation of the eyes must be
injurious to any animal, and as eyes are certainly
not indispensable to animals with subterranean
habits, a reduction in their size, with the adhesion
of the eyelids and growth of fur over them,
might, in such case, be an advantage; and if so,
Natural Selection would constantly aid the effects
of disuse. It is well known that several
animals, belonging to the most different classes,
which inhabit the caves of Styria and of
Kentucky, are blind. In some of the crabs, the
foot-stalk for the eye remains, though the eye is
gone; the stand for the telescope is there,
though the telescope with its glasses has been
lost. As it is difficult to imagine that eyes,
though useless, could be in any way injurious to
animals living in darkness, Mr. Darwin attributes
their loss wholly to disuse. Not a single
domestic animal can be named which has not, in
some country, drooping ears; and the view
suggested by some authors, that the drooping is
due to the disuse of the muscles of the ear from
the animals not being much alarmed by danger,
is accepted as probable.

Mr. Wollaston has discovered the remarkable
fact that two hundred kinds of beetles, out of the
five hundred and fifty inhabiting Madeira, cannot
fly; and that of the twenty-nine endemic genera,
no less than twenty-three genera have all their
species in this condition. Several facts, namely,
that beetles, in many parts of the world, are
frequently blown to sea and perish; that the
beetles in Madeira, as observed by Mr.
Wollaston, lie much concealed until the wind lulls
and the sun shines; that the proportion of
wingless beetles is larger on the exposed
Desertas than in Madeira itself; and especially
the extraordinary fact, so strongly insisted on
by Mr. Wollaston, of the almost entire absence
of certain large groups of beetles, elsewhere
excessively numerous, and which groups have
habits of life almost necessitating frequent
flight;—these several considerations have made
Mr. Darwin believe that the wingless condition
of so many Madeira beetles is due mainly to the
action of natural selection, but combined
probably with disuse. For, during thousands of
successive generations, each individual beetle
which flew least, either from its wings having
been ever so little less perfectly developed, or
from indolent habit, will have had the best
chance of surviving from not being blown out to
sea; and, on the other hand, those beetles
which most readily took to flight would oftenest
have been blown to sea and thus have been
destroyed. As with mariners shipwrecked near a
coast, it would have been better for the good
swimmers if they had been able to swim still
further, whereas it would have been better for