FACT OF VARIATION.
It is scarcely possible to survey the members of the external world
around us without being struck with the instability with which
everything is impressed. The very shadows, as they pass, leave a moral
lesson behind them on the mountain-slope, which the student of Nature
would do well to contemplate. Whatever be our preconceived ideas of
the "immutability of the universe," from first to last the same truth
is re-echoed to our mind,--that here all is change. Organic and
inorganic matter are alike subjected to renovation and decay; and,
dependent on that general law, _variability_ within specific limits
would seem to be an almost necessary consequence. In the animal and
vegetable kingdoms, this principle of fluctuation is peculiarly
apparent; and not more surely do the winds of heaven ruffle the
forests over which they rage, than does the ebb and flow which is
perpetually going on amongst created things mar their boasted
constancy.
The _fact_ of aberration, to which we would briefly allude in this
chapter, requires but little comment; it is patent _a priori_. As a
matter of experience, every observer who has spent a week in the field
of Nature knows it to exist. However difficult it may be, in some
instances, to distinguish aright between species and varieties, as
rigidly defined, there is an instinct within us which often recognizes
the _latter_, even at first sight, as unmistakeably such: and in these
cases, a well-educated eye, although of course occasionally deceived,
will not often be found to err.
In the vegetable world this proneness to variation is self-evident;
and botanists innumerable, who have investigated the _causes_ on which
the modifications of certain plants have been presumed to depend, have
not been behindhand in acknowledging it. Soil, climate, altitude, and
a combination of other circumstances and conditions, have been
successively taken into account, and to each an amount of disturbing
influence (more or less, as the case may be) has been conceded. "The
more powerful agents," writes Professor Henfrey, "enforce their
general laws, but every little local action asserts its qualifying
voice; and we see that all these irregularities and uncertainties (as
we in our ignorance call them, and complain of) are necessary and
important parts of a great whole,--are but isolated features of a
comprehensive plan, in accordance with which all work in concert to
bring about that _change_ absolutely indispensable to the existence of
animal and vegetable life upon the earth's surface, and that _variety
of conditions_ by which is ensured a fitting abode for each kind of
its multifarious and diversified inhabitants."
Whilst exploring the barren moor, or bleak upland heights, the
botanist would as assuredly look for a change in the outward
configuration of certain species, which colonize equally the rich
meadows and teeming ravines, as a geographical difference is _a
priori_ anticipated between the hard, sturdy mountaineer and the more
enervated denizen of the plain. A daisy, gathered on the cultivated
lawn, has usually attained a greater degree of perfection and
luxuriance than its companion from the sterile heath; and the bramble
which chokes up the ditches of the sheltered hedgerow, wears a very
different aspect from its stunted brother of the hills.
Nor is this dependency on external circumstances less apparent in the
animal kingdom also,--the domesticated races of which every
agriculturist is aware are capable of modification, artificially, to
an almost unlimited extent; and which exhibit, when even in a state of
nature, nearly as great a variety, from purely natural causes, as they
have been proved to do when subjected to the laws and routine of
agrarian science. Take the sheep, for example, of Dartmoor or Wales,
and compare them with those from the wolds of Lincolnshire and the
downs of Kent; or contrast the Hereford oxen with those of the midland
counties, or of the Caledonian breed, still extant in Cadzow Forest,
and it will require but little argument to convince us how important
is the operation of local circumstances in regulating the outward
contour of these higher creatures. If therefore this general obedience
to influences from without be self-evident in the vegetable world, and
equally traceable amongst the Mammalia, why, we may ask, are the
lower members of the animal creation to be denied analogous effects
from the same causes?
We are often told that the Annulosa present so many anomalies in their
organization, that we cannot apply the argument of analogy, when
reasoning on their structure and attributes; and that we must
consequently be content to leave it an open question, as to whether or
not they possess anything in common with the Vertebrata, or can be
presumed to be acted upon, by external agencies, in at all a similar
manner. Now, whilst there is clearly some truth in this assertion
(especially as regards the _senses_ of insects, which must ever remain
a subject of obscurity), I contend that to accept it in all its
fullness would be in the highest degree unphilosophical; whilst, to
endorse it to the extent which even its partial advocates do insist
upon, would at once involve us in a host of difficulties (affecting
other departments of natural science), the very existence of which
they have themselves tacitly repudiated.
"Creation," says one of our most intelligent writers of modern times,
"_is full of analogies_, pointing to one general originator, and
linking all sentient things into one great family of related
fellow-creatures:"--and there is an amount of sagacity in the remark
which it would be wise for us to digest. Throughout the whole of
animated nature, it is impossible not to perceive that certain
circumstances do, in the main, produce certain results. They may often
fail to produce them, and the results themselves may frequently be
modified (or, apparently, even reversed), from counter influences of
divers kinds. This touches not, however, the existence of the law; and
the effect is not the less specifically dependent on its own peculiar
cause, because those "counter influences" prevail,--and because
_different_ effects may chance, therefore, to be occasionally brought
about by causes which may possibly _seem_ to be identical. We should,
rather, bear in mind that the agents which operate in moulding the
outward contour of organic beings are various, and capable _inter se_
of permutations innumerable; so that it is only on a broad scale that
parallel results can be looked for in creatures severally exposed to
the action of elements, which are _liable_ to be differently
compounded from what may _prima facie_ appear to be the case: and
that, consequently, where opposite phaenomena are displayed under
circumstances seemingly coincident, our first object should be (_not_
to regard the phaenomena as indicative, that no constant result can be
anticipated from causes which are similar, but), to inquire whether
the circumstances in question _are_ really coincident or not,--seeing
that some counteracting stimulus may have been, here or there,
unexpectedly at work, which shall enable us, so soon as it is
detected, to account for the discrepancy.
It is by this process alone that we can hope to make real use of
analogy, without abusing it: for whilst there is danger, on the one
hand, of needlessly rejecting the argument which it suggests to us,
through opposite effects being observed (amongst the members of the
organic world) from conditions which _we assume to be_ co-ordinate,
but which in fact are not so; we may, on the other, run a similar risk
(and thus fail to discern a _corresponding modus operandi_ in the
maturation of like results), from a mere _a priori_ belief that the
lower animals cannot be acted upon, by external influences, in a
manner at all equivalent to that which is self-evident in the higher
ones.
"To make a perfect observer in any department of science," writes Sir
John Herschel, "an extensive acquaintance is requisite, not only with
the particular science to which his observations relate, but with
every branch of knowledge which may enable him to appreciate and
neutralize _the effect of extraneous disturbing causes_. Thus
furnished, he will be prepared to seize on any of those minute
indications which often connect phaenomena which seem quite remote from
each other. He will have his eyes as it were opened, that they may be
struck at once with any occurrence which, according to received
theories, ought _not_ to happen; for these are the facts which serve
as clews to new discoveries[1]."
There can be no doubt that amongst a large proportion of our
naturalists, _differences_, as such, are too exclusively studied.
Essential as their investigation is (for we could not progress a step
without some presumptive notion as to the specific identity, or not,
of the objects about which we have to treat), we should not forget
that there are other questions, likewise, which ought to occupy our
attention in, at any rate, an almost equal degree,--as being of
eminent significance in guiding us to a correct interpretation of the
phaenomena with which we have to deal. Such are, more especially,
similitudes and analogies, in their widest sense,--which are too often
neglected, even by those who admit the necessity of recognizing them
where they may be shown to exist. Lord Bacon, in referring to a
similar tendency amongst a certain section of the naturalists of his
day, remarks (though perhaps his love of analogies may have led him to
somewhat overrate their importance): "Up to this time the industry of
men has been great, and very curious in marking the variety of things,
and explaining the accurate differences of animals, herbs, and
fossils,--the _chief part of which_ are the mere sport of Nature,
rather than serious and of use toward the sciences. Such things tend
to our enjoyment, and sometimes to even practical use; but little or
nothing towards an insight into Nature. And so our labour is to be
turned to inquiry into, and notice of, similitudes and analogies, both
in the whole and in the parts of things: for these are they which
unite Nature, and begin to establish sciences[2]."
I believe that, if analogies were more carefully studied in the lower
departments of the animal kingdom, we should be less inclined to deny
some sort of uniformity to the action of elements and conditions
which, by a law of Nature, must at times operate equally upon the
various and dissimilar members of the organic creation. Amongst the
Insecta, where the individuals exist in such multitudes that accuracy
in generalizations concerning them, becomes, as it were, peculiarly
within our reach, this doctrine cannot be too rigidly insisted upon;
and it is not difficult to foresee that, should the principle of
external disturbing influences ever be admitted by entomologists to
the extent which it has been accepted by the students of the
Vertebrata, our so-called "species" will have to submit to a process
of elimination and inquiry, which at present would be well nigh
incredible. The time for such a step is yet far off: perhaps indeed,
considering the innovations of nomenclature which it would
necessitate, it will never arrive at all; yet the fact remains the
same, that, _if_ analogy with creatures of a more perfect development
be not altogether disallowed us, during our researches into the insect
tribes, or _if_ similar causes may be presumed to have somewhat
similar effects in opposite sections of the animate world, an
enlargement of our prescribed limits, for specific variation, ought in
reality to follow (sooner or later) as an inevitable consequence.
In whichever light, therefore, insect aberration is viewed by
us,--whether as a matter of experience (which, being self-evident,
will satisfy the practical observer), or as probable from analogy
(which will hardly be denied, at any rate to a certain extent, by even
the most theoretical),--we affirm that _it does, ipso facto, exist_.
"There is no similitude in Nature that owneth not _also to a
difference_;" let this be constantly borne in mind, for it is a truism
almost beyond controversy, and one which, to a reflective mind, will
scarcely admit of a doubt.
It will be perceived, from the above remarks, that I draw a
distinction between insects which simply vary (that is to say, which
aberr from their normal state), and those which afford (in
the sense as enunciated in the last chapter) one or more actual
"varieties,"--technically so called and it will be further gathered,
that, whilst I regard the former as universally to be met with, the
latter are, on the contrary, of only occasional occurrence. That
positive and well-defined varieties, or races, should be confined to
certain species, is not remarkable; but that every individual insect
should differ, however slightly, from its nearest relation and ally,
may perhaps require some few words of explanation, even to a
naturalist. It is not essential however to our present subject (which
is merely a plea for specific variation generally, as commonly
understood) that any such dogma should be propounded; nevertheless,
since all analogy teaches us to anticipate it, and observation tends
more and more, as our knowledge advances, to corroborate the fact, I
shall be pardoned for venturing a passing thought upon a question even
thus difficult of demonstration.
Perhaps we are too prone to regard those specific characters, which
are so subtle that they cannot be grasped by our clumsy faculties
except in their broadest and plainest features, as incapable of
fluctuation. Yet a practised eye can detect discrepancies innumerable
in specimens which appear absolutely alike to one that is uneducated;
whilst a third person, better qualified still, will trace out other
and more delicate distinctions, with even greater precision. And thus
it is that we rise, step by step, even amongst the humbler
representatives of the animal kingdom, to the comprehension of that
great truth which is so conspicuous in the nobler ones, and which we
have already summoned to our aid, that "there is no similitude in
Nature which owneth not also to a difference." Let us not forget that
the sphere of our senses is limited; and that, although tuition will
do much to enlarge their capacity for perception, we are at the best
but a dim-sighted race: hence, we should be careful to avoid
conclusions which are not warranted by analogy, and which our
understanding, as it becomes gradually brighter, no less assuredly
condemns. True it is, that we may not be able, as in the higher
animals, to appreciate the differences between individuals without a
rigid inspection, and that sometimes we may fail to do so even when
the objects are critically examined; yet the fact that new
peculiarities do unquestionably open out upon us, as we become more
and more trained for the recognition of them, ought to warn us that
others _may_ exist likewise, despite our _prima-facie_ conclusions;
whilst analogy with what we know to be the case in other departments
of the organic world should suggest, unless indeed there is
presumptive evidence to the contrary, that they in all probability
_do_.
The Alpine range, when seen from afar, appears a monotonous mass of a
dull uniform hue; and nothing, of all the wondrous details which it
includes, can be distinguished, except perchance the outline of its
jagged peaks projected in faint relief against the distant sky. One by
one, however, as we approach it, inequalities present themselves; the
surface which lately seemed so uniform and grey that it could be
compared only to a cloud, is found to be cleft by ravines; and
valleys, in all their magnificence and breadth, expand slowly to our
view. Yet, marvellous as is the change, this is not all: wood and
water, without which the landscape would be barren, are in turn
revealed; whilst the play of light and shade upon the mountain-slopes
proclaims at length that the picture is well nigh complete. Still more
to be disclosed does in reality remain; and we must advance nearer yet
if we would either fully realise the whole, or enter into the
surprising minutiae of each of its component parts. And so it is with
the objects which we have been just discussing. When contemplated in a
mass, and by an uneducated eye, hosts of them may appear to be
identical; but as our vision becomes clearer and more acute,
differences, formerly inappreciable, are gradually made
manifest,--until at last we can detect modifications innumerable,
throughout the entire length of the living panorama; and are enabled
to endorse the belief (repugnant _a priori_ though it be), that
_individual variations_, even to the extent which I have ventured to
suggest, are not incompatible with _specific similitudes_.
FOOTNOTES:
[1] Preliminary Discourse on the Study of Natural Philosophy (London,
1830), p. 132.
[2] "Magna enim hucusque atque adeo curiosa fuit hominum industria, in
notanda rerum varietate, atque explicandis accuratis animalium,
herbarum, et fossilium differentiis; quarum pleraeque magis sunt lusus
naturae, quam seriae alicujus utilitatis versus scientias. Faciunt certe
hujusmodi res ad delectationem, atque etiam quandoque ad praxin; verum
ad introspiciendam naturam parum aut nihil. Itaque convertenda plane
est opera ad inquirendas et notandas rerum similitudines et analoga,
tam in integralibus, quam partibus: illae enim sunt, quae naturam
uniunt, et constituere scientias incipiunt."--_Novum Organum_, lib.
ii. 27.