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The Darwinian Hypothesis
by Thomas H。 Huxley
DARWIN ON THE ORIGIN OF SPECIES。
THERE is a growing immensity in the speculations of science to which no
human thing or thought at this day is comparable。 Apart from the
results which science brings us home and securely harvests； there is an
expansive force and latitude in its tentative efforts； which lifts us
out of ourselves and transfigures our mortality。 We may have a
preference for moral themes； like the Homeric sage； who had seen and
known much：
〃Cities of men
And manners； climates； councils； governments〃；
yet we must end by confession that
〃The windy ways of men
Are but dust which rises up
And is lightly laid again；〃
in comparison with the work of nature； to which science testifies； but
which has no boundaries in time or space to which science can
approximate。
There is something altogether out of the reach of science； and yet the
compass of science is practically illimitable。 Hence it is that from
time to time we are startled and perplexed by theories which have no
parallel in the contracted moral world； for the generalizations of
science sweep on in ever…widening circles； and more aspiring flights；
through a limitless creation。 While astronomy； with its telescope；
ranges beyond the known stars； and physiology； with its microscope； is
subdividing infinite minutiae； we may expect that our historic
centuries may be treated as inadequate counters in the history of the
planet on which we are placed。 We must expect new conceptions of the
nature and relations of its denizens； as science acquires the materials
for fresh generalizations； nor have we occasion for alarms if a highly
advanced knowledge； like that of the eminent Naturalist before us；
confronts us with an hypothesis as vast as it is novel。 This
hypothesis may or may not be sustainable hereafter； it may give way to
something else； and higher science may reverse what science has here
built up with so much skill and patience； but its sufficiency must be
tried by the tests of science alone； if we are to maintain our position
as the heirs of Bacon and the acquitters of Galileo。 We must weigh
this hypothesis strictly in the controversy which is coming； by the only
tests which are appropriate； and by no others whatsoever。
The hypothesis to which we point； and of which the present work of Mr。
Darwin is but the preliminary outline； may be stated in his own
language as follows：〃Species originated by means of natural
selection； or through the preservation of the favoured races in the
struggle for life。〃 To render this thesis intelligible； it is
necessary to interpret its terms。 In the first place； what is a
species？ The question is a simple one； but the right answer to it is
hard to find； even if we appeal to those who should know most about
it。 It is all those animals or plants which have descended from a
single pair of parents； it is the smallest distinctly definable group
of living organisms； it is an eternal and immutable entity； it is a mere
abstraction of the human intellect having no existence in nature。 Such
are a few of the significations attached to this simple word which may
be culled from authoritative sources； and if； leaving terms and
theoretical subtleties aside； we turn to facts and endeavour to gather a
meaning for ourselves； by studying the things to which； in practice；
the name of species is applied； it profits us little。 For practice
varies as much as theory。 Let the botanist or the zoologist examine and
describe the productions of a country； and one will pretty certainly
disagree with the other as to the number； limits； and definitions of
the species into which he groups the very same things。 In these
islands； we are in the habit of regarding mankind as of one species； but
a fortnight's steam will land us in a country where divines and
savants； for once in agreement； vie with one another in loudness of
assertion； if not in cogency of proof； that men are of different
species； and； more particularly； that the species negro is so distinct
from our own that the Ten Commandments have actually no reference to
him。 Even in the calm region of entomology； where； if anywhere in this
sinful world； passion and prejudice should fail to stir the mind； one
learned coleopterist will fill ten attractive volumes with descriptions
of species of beetles； nine…tenths of which are immediately declared by
his brother beetle…mongers to be no species at all。
The truth is that the number of distinguishable living creatures almost
surpasses imagination。 At least a hundred thousand such kinds of
insects alone have been described and may be identified in collections；
and the number of separable kinds of living things is under estimated
at half a million。 Seeing that most of these obvious kinds have their
accidental varieties； and that they often shade into others by
imperceptible degrees； it may well be imagined that the task of
distinguishing between what is permanent and what fleeting； what is a
species and what a mere variety； is sufficiently formidable。
But is it not possible to apply a test whereby a true species may be
known from a mere variety？ Is there no criterion of species？ Great
authorities affirm that there isthat the unions of members of the
same species are always fertile； while those of distinct species are
either sterile； or their offspring； called hybrids； are so。 It is
affirmed not only that this is an experimental fact； but that it is a
provision for the preservation of the purity of species。 Such a
criterion as this would be invaluable； but； unfortunately； not only is
it not obvious how to apply it in the great majority of cases in which
its aid is needed； but its general validity is stoutly denied。 The
Hon。 and Rev。 Mr。 Herbert； a most trustworthy authority； not only
asserts as the result of his own observations and experiments that many
hybrids are quite as fertile as the parent species； but he goes so far
as to assert that the particular plant 'Crinum capense' is much more
fertile when crossed by a distinct species than when fertilised by its
proper pollen！ On the other hand； the famous Gaertner； though he took
the greatest pains to cross the primrose and the cowslip； succeeded
only once or twice in several years； and yet it is a well…established
fact that the primrose and the cowslip are only varieties of the same
kind of plant。 Again； such cases as the following are well
established。 The female of species A； if crossed with the male of
species B； is fertile； but； if the female of B is crossed with the male
of A； she remains barren。 Facts of this kind destroy the value of the
supposed criterion。
If； weary of the endless difficulties involved in the determination of
species； the investigator； contenting himself with the rough practical
distinction of separable kinds； endeavours to study them as they occur
in natureto ascertain their relations to the conditions which
surround them； their mutual harmonies and discordances of structure；
the bond of union of their parts and their past history； he finds
himself； according to