The Darwinian Hypothesis | Page 5

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 nature--to 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
the received notions, in a mighty maze, and with, at most, the dimmest
adumbration of a plan. If he starts with any one clear conviction, it is
that every part of a living creature is cunningly adapted to some special
use in its life. Has not his Paley told him that that seemingly useless
organ, the spleen, is beautifully adjusted as so much packing between
the other organs? And yet, at the outset of his studies, he finds that no

adaptive reason whatsoever can be given for one-half of the
peculiarities of vegetable structure; he also discovers rudimentary teeth,
which are never used, in the gums of the young calf and in those of the
foetal whale; insects which never bite have rudimental jaws, and others
which never fly have rudimental wings; naturally blind creatures have
rudimental eyes; and the halt have rudimentary limbs. So, again, no
animal or plant puts on its perfect form at once, but all have to start
from the same point, however various the course which each has to
pursue. Not only men and horses, and cats and dogs, lobsters and
beetles, periwinkles and mussels, but even the very sponges and
animalcules commence their existence under forms which are
essentially undistinguishable; and this is true of all the infinite variety
of plants. Nay, more, all living beings march side by side along the
high road of development, and separate the later the more like they are;
like people leaving church, who all go down the aisle, but having
reached the door some turn into the parsonage, others go down the
village, and others part only in the next parish. A man in his
development runs for a little while parallel with, though never passing
through, the form of the meanest worm, then travels for a space beside
the fish, then journeys along with the bird and the reptile for his fellow
travellers; and only at last, after a brief companionship with the highest
of the four-footed and four-handed world, rises into the dignity of pure
manhood. No competent thinker of the present day dreams of
explaining these indubitable facts by the notion of the existence of
unknown and undiscoverable adaptations to purpose. And we would
remind those who, ignorant of the facts, must be moved by authority,
that no one has asserted the incompetence of the doctrine of final
causes, in its application to physiology and anatomy, more strongly
than our own eminent anatomist, Professor Owen, who, speaking of
such cases, says ('On the Nature of Limbs', pp. 39, 40): "I think it will
be obvious that the principle of final adaptations fails to satisfy all the
conditions of the problem."
But, if the doctrine of final causes will not help us to comprehend the
anomalies of living structure, the principle of adaptation must surely
lead us to understand why certain living beings are found in certain
regions of the world and not in others. The palm, as we know, will not
grow in our climate, nor the oak in Greenland. The white bear cannot

live where the tiger thrives, nor 'vice versa', and the more the natural
habits of animal and vegetable species are examined, the more do they
seem, on the whole, limited to particular provinces. But when we look
into the facts established by the study of the geographical distribution
of animals and plants it seems utterly hopeless to attempt to understand
the strange and apparently capricious relations which they exhibit. One
would be inclined to suppose 'a priori' that every country must be
naturally peopled by those animals that are fittest to live and thrive in it.
And yet how, on this hypothesis, are we to account for the absence of
cattle in the Pampas of South America, when those parts of the New
World were discovered? It is not that they were unfit for cattle, for
millions of cattle now run wild there; and the like holds good of
Australia and New Zealand. It is a curious circumstance, in fact, that
the animals and plants of the Northern Hemisphere are not only as well
adapted to live in the Southern Hemisphere as its own autochthones,
but are in many cases absolutely better adapted, and so overrun and
extirpate the aborigines. Clearly, therefore, the species which naturally
inhabit a country are not necessarily the best adapted to its climate and
other conditions. The inhabitants of islands are often distinct from any
other known species of