Animal Life and Intelligence

by C. Lloyd Morgan

The fact that the special characteristics of the male, which we have seen to be variable in the ruff, are also variable among insects, is well exemplified in the case of the stag-beetle, in some males of which the mandibles are far larger than in others. This is shown in [Fig. 22], which is copied from the series displayed in the British Museum, by the kind permission of Professor Flower.

Fig. 22.—Variations in the size of, and especially in the head and mandibles of, the male stag-beetle (Lucanus cervus). (From an exhibit in the British Natural History Museum.)]

Crossing the hall to where the vertebrate structures are displayed, the development of hair, of feathers, of teeth, the modifications of the skull and of legs, wings, and fins are being exemplified. Note here and elsewhere the special adaptations of structure, of which we may select two examples. The first is that seen in the Balistes, or trigger-fish. The anterior dorsal fin is reduced to three spines, of which that which lies in front is a specially modified weapon of defence, while that which follows it is the so-called trigger. These two are so hinged to the underlying interspinous bones and so related to each other that, when once the defensive spine in front is erected, it cannot be forced down until the trigger is lowered. The second example of special adaptation is well displayed in specimens of the mud-tortoise Trionyx. Between the last vertebra of the neck and the first fixed vertebra of the dorsal series is a beautiful hinge-joint, enabling the neck to be bent back, S-fashion, when the creature withdraws its head within the carapace. These are only one or two particular instances of what any one who will visit the National Museum may see for himself admirably displayed and illustrated.

No one can, one would suppose, pass through the galleries in Cromwell Road and remain quite insensible to the beauties of animal life. Beauty of form and beauty of colour are conspicuously combined in many species of birds and insects. And much of this colour-beauty and splendid iridescence is known to be due to minute scales, to thin films of air or fluid, and to microscopically fine lines developed upon scales or feathers. But there is one phase of beauty which cannot be exhibited in the museum—the beauty that comes of life as opposed to death. For this we must go out into the free air of nature, where the animals not only have lived, but are still instinct with the glow of life, and where the silence of the museum galleries is replaced by the song of birds and the hum of insect-wings.

How have this wealth, this diversity, this beauty, this manifold activity, which we summarize under the term "animal life," been produced?

If we answer this question in a word—the word "evolution"[CI]—we must remember that this word merely expresses our belief in a general fact; and we must not forget that many questions remain behind, all centering round that little question, to which an adequate answer is so difficult to give, the question—How? Reduced to its simplest expression, the doctrine of evolution merely states that the animal world as it exists to-day is naturally developed out of the animal world as it existed yesterday, and will in turn develop into the animal world as it shall exist to-morrow. This is the central belief of the evolutionist. No matter what moment in the past history of life you select, the life at that moment was in the act of insensibly passing from the previous towards a future condition. Then at once arises the question—Does life remain the same yesterday, to-day, and to-morrow? A thousand indubitable facts at once make answer—No! Underlying the law of continuity there is a law of change. Life to-day is not what it was yesterday, nor will it be to-morrow the same as to-day. What, then, is the nature of this change? If it be replied that the change must be either for the better or the worse, we shall have to answer the further question—Better or worse in what respects?

Let us narrow our view from the contemplation of life as a whole to the more particular consideration of an organism as one of its constituent units. The individual life of that organism depends on (some would say consists in) its ceaseless adaptation to surrounding circumstances. The circumstances remaining the same, or only varying within constant limits, the adaptation may be more or less perfect. A change in the direction of more perfect adaptation will be a change for the better, a tendency to less perfect adaptation will be a change for the worse.

But the relation of an organism to its circumstances or environment is itself subject to change. The environment itself may alter, or the organism may be brought into relation with a new environment. We have to consider not only the changes in an organism in the direction of more or less perfect adaptation to its environment, but also changes in the environment. These changes are in the direction of increased simplicity or of increased complexity. So that we may say that the modification of life is in the direction of more or of less complete adaptation to simpler or to more complex conditions. Where the adaptation advances to more complex conditions, we speak of elaboration; where it retrogrades to less complex conditions, we speak of degeneration; but both fall under the head of evolution in its more general sense. Viewed as a whole, there can be little doubt that the general tendency of evolution is towards more complete adaptation to more diverse and complex environment. And this tendency is accompanied by a general increase of differentiation and of integration; of differentiation whereby the constituent elements of life, whether cells, tissues, organs, organisms, or groups of organisms, become progressively more specialized and more different from one another; of integration whereby these elements become progressively more interdependent one on the other. We may conveniently sum up the tendency towards more perfect adaptation to more complex circumstances in the word progress; the tendency to differentiation in the word individuality; and the tendency to integration in the word association.