Zomer 2009 no. 67
The Dutch Dickensian Volume XXIX 54
Cbarlöi Dickens.] ALL THE
another, of pouched animals in. another, of a
peculiar modification of leaves iu Australian
shrubs, of peculiar aloes or agaves in America
i are inexplicable on the theory of creation.
Glancing at instincts, marvellous as some are,
they offer, it appears, no greater difficulty than
does corporeal structure, on the theory of the
i Natural Selection of successive, slight, bijt pro-
j Stable, modifications. We can thus understand
I why nature moves by graduated steps in endow
ing' different animals of the same class with their
several instincts. On the view of all the spe
cies of the same genus Slaving descended from
a common parent, and having inherited much in
j common, we can understandhow it is that allied
I species, when placed under considerably differ
ent conditions of life, yet should follow nearly
the same instincts; why the male wrens of
North America, for instance, build cock-nests"
j to roost in, like the males of our distinct kitty-
wrensa habit wholly unlike that of any other
i known bird. On the view of instincts having
been slowly acquired through Natural Selection,
we need not marvel at some instincts being ap
parently not perfect, but liable to mistakes, as
when blow-flies lay their eggs in the carrion-
scented flowers of stapelias; nor at many in-
1 stiucts causing other animals to suffer, as when
1 ants make slaves of their fellow-ants, when the
i larvre of ichneumon flies feed within the live
|i bodies of caterpillars, and when the nestling
i cuckoo ungratefully ejects his legitimate foster-
brethren out of the family nest.
Instincts are as important as bodily structure
for the welfare of each species, uuder the condi
tions of life by which it happens to be sur
rounded. Under changed circumstances, it is
possible that slight modifications of instinct,
might be profitable to a speciesand if it can
be shown that instincts do vary ever so little,
then. Mr. Darwin sees 110 difficulty in Natural
Selection preserving and continually aeeumu-
j lating variations of instinct to any extent that
may be profitable. Ilis line of argumentand
1 the whole volume is one long argumentmay
be summed up in this give him an inch, and he
1takes an ell. Instincts certainly do varyfor in
stance, the migratory instinct varies, both in ex
tent and direction, and in its total loss. So it is
with the nests of birds, which vary partly in
dependence on the situations chosen and on the
nature and temperature of the country inha
bited, but often from causes wholly unknown to
us. It is thus, he believes, that all the most
complex and wonderful instincts have origi
nated; although 11Ö complex instinct can pos
sibly be produced except by the slow and gra
dual accumulation of numerous slight, yet pro-
Stable, variations, requiring ages upon ages, and
I tens of thousands, perhaps hundreds of millions,
of generations to work them out. Eor Mr.
Darwin assumes such au inconceivably vast
period of lapsed time for the accomplishment of
his theory, t hat it is simply not eternity, because
it had a beginning.
Variations of instinct, thus acquired, become,
in races, habitual and hereditary. Habit and
HOUND. .[j»iy 7, moo 395
the selection of so-called accidental variations,
have played important parts in modifying the
mental qualities of our domestic animals. It
cannot, be doubted that young pointers will
sometimes point, and even back other dogs, the
very first time that they are taken out; retriev
ing is certainly in some degree inherited by
retrieversas is a tendency to run round, ia- i
stead of at, a flock of sheep by shepherds' dogs, j
These actions do not differ essentially from true
instincts; for the young pointer can no more
know that he points to aid his master, than the
white butterfly knows why she lays her eggs on
the leaf of the cabbage. How strongly these
habits and dispositions are inherited, and how
curiously ihey become mingled, is well shown
when different breeds of dogs are crossed. A I
cross with the greyhound has given to a whole i
family of shepherds' dogs, the lurchers, a ten-
dency to hunt hares, rendering them invaluable
to poachers. Le Hoy describes a dog whose j
great-grandfather was a wolf, and this dog j
showed a trace of its wild parentage only in one
wayby not coming in a straight line to his j
master when called.
To understand how instincts in a state of
nature have become modifled by Natural Selec
tion, let us consider the case of the cuckoo. It
is commonly admitted that the more immediate
and final cause of the cuckoo's instinct is that
she lays her eggs, not daily, but at intervals of 1
two or three daysso that, if she were to make
her own nest and sit on her own eggs, those j
first laid would have to be left for some time
uninoubated, or there would be eggs, and young
birds of different ages iu the same nestwhich
would make the process of laying, hatching, and
rearing the young, inconveniently long and
troublesome. The American cuckoo makes her
own nest, and has eggs and young successively
hatched, all at the same time.
Now, instances can be given of various birds
which have been known occasionally to lay
their eggs in other birds'nests. Let us sup- ij
pose that the ancient progenitor of our Euro-
pean euekoo had the habits of the American
cuckoo, but that she occasionally laid an egg in j
another bird's nest by way of experiment. If
the old bird profited by this occasional habit, or
if the young were made more vigorous by the
mistaken maternal instinct of another bird than
by their own mother's care, encumbered as she
can hardly fail to be by having eggs and young of
different ages at the same time, then the old
birds, or the fostered young, would gain an ad
vantage. And analogy leads Mr. Darwin to be
lieve that the young thus reared would be apt j
to follow, by inheritance, the occasional and j
aberrant habit of their mother, and in their
turn would possibly lay their eggs in other
birds' nests, and thus be successful in rearing
their young. By a continued process of this
nature, he believes that the strange instinct of
our cuckoo could be, and has been, generated.
To Mr. Darwin, ibis explanation appears con- J
elusiveoilier persons, less under Ac influence
of a fixed idea, may observe that, with the help j
