Zomer 2009 no. 67
57
The Dutch Dickensian Volume XXIX
I 29S [J«dr 7, is®.] ALL THE
i each man trying to keep the best clogs without
any thought of modifying the breed.
1Eren without any change in the proportional
numbers of the animals 011 which our wolf
preyed, a cub might be bora with an innate ten
dency to pursue certain kinds of prey. Nor can
this be thought very improbable for wo often
observe great differences in the natural tenden
cies of our domestic animalsone eat, for in
stance, taking to catching rats, another mice;
one cat, according to Mr, St. John, bringing
home winged game, another bares, or rabbits,
and another hunting on marshy ground and
almost nightly catching woodcocks or snipes.
The tendency lo 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 pro
cess, a new variety might, be formed which would
I 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 lo hunt
different prey; and from Ike continued pre
servation of the individuals best fitted for the
two sites, two varieties might be slowly formed.
According to Mr. Pierce, there arc two varieties
j of the wolf inhabiting the Catskill Mountains
in the United States one with a light grey
hound-like form, which pursues deer, and tie
1 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 se
lection, in the modification of species; use
f strengthens and enlarges certain parts, and dis-
use diminishes them. Such modifications are
inherited. Many animals have structures which
ican 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
i prey, has been caused by disuse. The ostrich,
indeed, inhabits continents, and is exposed to
danger from which it cannot escape by flight;
I but by kicking it can defend itself from its
j enemies, as well as any of the smaller quad-
j rupeds. "We may imagine that the early pro
genitor of the ostrich had habits like those
of a bustard, and üiat as Natural Selection in-
creased 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 iu size, arid in some
j cases are quite covered up by skin aud fur.
1 This state of the eyes is probably due to gradual
reduction, from disuse, but aided, perhaps, by
Alt ROUND. tCondactad Ey f
Natural Selection. 111 South America, a burrow- j
ing rodent, the tuco-taco, is even more suhter- j
ran can in its habits than the mole and the Spa- i
niards, who often catch them, assert that they
are frequently blind. One, which Mr. Darwin j
kept- alive, was certainly in this condition, the f
cause, as appeared on dissection, having "been
inflanunation of the nictitating membrane. As 1
frequent inflammation of the eyes must be inju- 1
rious to any animal, and as eyes are certainly
not indispensable to animals with subterranean
habits, a reduction in their size, with the adhe
sion of the eyelids and growth of fur over them, j
might, in such case, be an advantage and if so, I
Natural Selection would constantly aid the effects j
of disuse. It is well known that several ani-
mals, belonging to the most different classes,
which inhabit the caves of Styria and of Ken
tucky, are blind. I11 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 bo in any way injurious to j
animals living in darkness, Mr. Darwin altri- I
butes their loss wholly to disuse. Not a single
domestic animal can be named which has not, in
some country, drooping earsand the view sug- i
gested 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. Vollaston has discovered the remarkable
faefc that two hundred kinds of beetles, out of the i
five hundred and Jifty inhabiting Madeira, cannot
flyand that of the twenty-nine endemic genera,
no less than twenty-three genera have all their
species in tliis condition. Several facts, namely,
that beetles, in many parts of the world, arc
j frequently blown to sea and perishthat the
beetles iu Madeira, as observed by Mr. Vol
kston. lie much concealed until the wind lulls
and the sun shines; that the proportion of
wingless beetles is larger 011 the exposed
Desertas than in Madeira itself; and especially
the extraordinary fact, so strongly insisted on j
by Mr. Volkston, of the almost entire absence
oi' certain large groups of beetles, elsewhere ex-
cessively numerous, and which groups have
habits of life almost necessitating frequent
flightthese several considerations have made j
Mr. Darwin believe that, the wingless condition i'
of so many Madeira beetles is due mainly to ihe i
I action of natural selection, but combined pro- j
bably with disuse. Tor, 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 j
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 de
stroyed. As with mariners shipwrecked near a
coast, it would have been better for the good
swimmers if they had been able to swim still j
further, whereas it would have been better for
