Picture - Cosmic Polymath

PROFESSOR HUXLEY'S VIEWS ON EVOLUTION 203
§ 35. Professor Huxley's Views on Evolution, especially in connection with the Reptile, the Bird, and
the Horse.
Professor Huxley approaches the subject of evolution with considerable caution, and discusses it in his
"Lectures and Essays" with remarkable adroitness and skill. His utterances are characterised by great frank-
ness and lucidity of statement. He divides his argument in favour of evolution into two parts— one of which
may be said to be constructive, the other destructive. The constructive part of the argument is admirably put,
and with it I substantially agree. In the destructive part he is less satisfactory and convincing, and with it I find
myself ever and anon at issue.
It would occupy too much time and space to state his argument at length. I will therefore content myself
with liberal abstracts from it couched, for the most part, in his own incisive language.
His argument, it appears to me, is strongest where he deals with geologic types and with their persistency
and permanency in time and space ; and weakest where he attempts to set up connecting links, or, as he calls
them, sub-groups (intercalary forms), with a view to running together and merging the several types of animals.
In the sub-groups, the types themselves virtually disappear, even such distinct types as are represented by the
reptile and bird respectively.
These sub-groups, if sufficient time and space be allowed, are said gradually to displace the types, or, what
comes to the same thing, they run the types into each other, and so establish a line of descent and consanguinity.
In this way he refers the descent of the bird to the reptile and the one-toed horse to a remote five-toed ancestor.
If intermediary or intercalary forms be accepted, everything connected with evolution becomes possible. The
intermediary groups provide endless connecting links, and when they are absent they are assumed to exist as
" missing links," which is a very convenient arrangement for those who support the doctrine of evolution in its
entirety. Of course, it is very comforting to all such to be able to say, when an intermediate hnk is not forth-
coming, that it is a " missing hnk," and will be found sooner or later as science advances.
The destructive part of the argument, as indicated, has for its object to break down all outstanding differences
between animals (which is equivalent to the obliteration of types), and to set up a shding scale which merges, or
is calculated to merge, one animal into another. This is an insidious form of argument, and demolishes quietly, but
effectively, all distinctions, great and small.
The constructive part of the argument leads in quite another direction, and seeks to set up fundamental
distinctions, boundaries, order, and design.
While fully admitting that there are types of plants and animals adapted to special times and to particular
locahties, and that typical plants and animals in certain cases approach each other indefinitely near, I am not of
those who believe that all plants and all animals merge into each other by insensible gradations. I hold that the
fundamental differences between typical plants and animals cannot be got rid of by the introduction of hypo-
thetical intermediary groups, however numerous, and however quickly they follow each other. I hold, moreover,
that the theoretical intermediary groups or intercalary forms are assigned a much too important place in classi-
fication, and cannot logically be employed as reliable material in tracing the descent of the bird from the reptile
or the one-toed horse from an ancient five-toed ancestor.
The intermediary groups in animals (allowing they exist) display, in not a few cases, fewer modifications and
adaptations than are found in the limbs and traveUing organs, which, whatever the class of the animal, have rigidly
to conform to the requirements of land, water, and air transit. In the travelling organs there are what may be
designated connecting finks in locomotion, but no one thinks on this account of tracing the descent of the bird
and bat to the insect, the reptile to the fish, or the mammal to the reptile.
The flying lemur and flying lizard, in the matter of locomotion, connect the land with the air, and the flying
fish the water with the air ; but the flying lemur and flying hzard are not descended from or connected in any
way with the extinct pterodactyls. All that can be said is that both are flying creatures, and in this respect bear
a general resemblance to each other. The animals which live in the water must all conform to the fish type, and
display swimming tails, fins, flippers or webbed feet. The animals in question may be birds or mammals belonging
to entirely different families—that is, they are not connected by consanguinity and descent. Lastly, the flying
things may be insects, birds, or bats, and still further removed from each other as regards descent from a common
stock. The structural differences and modifications required in the walking, swimming, and flying organs are much
greater in many cases than exist between nearly related animals. I have consequently always felt that slight differences
in animals and animal structures are unduly magnified when they are intended to support evolution, much greater
differences being glossed over or altogether omitted when they do not favour that doctrine. The great subject
of locomotion, being opposed to the popular doctrine, is seldom referred to.