Animal Life and Intelligence

by C. Lloyd Morgan

It must not be supposed that these two modes of origin are mutually exclusive, and that any particular instinct must belong either to the one class or the other. On the contrary, many instincts have, as it were, a double root—the principle of selection combining with that of lapsing intelligence in the formation of a joint result. Intelligence may thus give a new direction to a primary instinct, and, the intelligent modification being inherited, what is practically a new instinct may arise. Conversely, selection may tend to preserve those individuals which perform some intelligent action, and may, therefore, aid the lapsing of intelligence in establishing and stereotyping an instinct.

Referring the reader to Mr. Romanes's work for the examples and illustrations by which he enforces his views, we may now proceed to consider the subject in the light of recently developed theories of heredity.

We have seen that a school of biologists has arisen who deny the inheritance of acquired characters. But Mr. Romanes's secondary instincts depend upon the inheritance of habits intelligently acquired. By the school of Professor Weismann, therefore (if we may so call it without injustice to Mr. Francis Galton), secondary instincts, in so far as any individual acquisition is concerned, are denied. Opposed to this school are those who lay great stress on the inheritance of acquired characters. Some of them seem driven to the opposite extreme in the matter of instinct, and appear to hold that instincts are entirely (or let us say almost entirely) due to lapsed intelligence. Professor Eimer, of Tübingen, for example, says,[IX] "I describe as automatic actions those which, originally performed consciously and voluntarily, in consequence of frequent practice, come to be performed unconsciously and involuntarily.... Such acquired automatic actions can be inherited. Instinct is inherited faculty, especially is inherited habit." In his discussion of the subject, Professor Eimer seems to make no express allusion to primary instincts. And he regards at any rate some of those which are classed by Mr. Romanes as primary, as due to lapsed intelligence. "Every bird," he says,[IY] "must, from the first time it hatches its eggs, draw the conclusion that young will also be produced from the eggs which it lays afterwards, and this experience must have been inherited as instinct." He says[IZ] that the infant takes the breast and sucks "in accordance with its acquired and inherited faculties." He believes[JA] that "the original progenitors of our cuckoo, when they began to lay their eggs in other nests, acted by reflection and with design." Regarding the mason-wasps and their allies, which sting larvæ in the ganglia which govern muscular action, and thus provide their young with paralyzed but living prey, he exclaims,[JB] "What a wonderful contrivance! What calculation on the part of the animal must have been necessary to discover it!" Of the storing instincts of bees he remarks,[JC] "Selection cannot here have had much influence, since the workers do not reproduce. In order to make these favourable conditions constant, insight and reflection on the part of the animals, and inheritance of these faculties, were necessary." And he concludes,[JD] "Thus, according to the preceding considerations, automatic action may be described as habitual voluntary action; instinct, as inherited habitual voluntary action, or the capacity for such action."

Professor Eimer would not probably deny the co-operation of natural selection in the establishment of these instincts, but he throws it altogether into the background. Now, such a view seems to me wholly untenable. Many of the instincts of insects are performed only once in the course of each individual life. Can it be supposed that the weaving of a cocoon by the caterpillar is mainly a matter of lapsed intelligence? Even if we credit the hen bird with the amount of reflection supposed by Professor Eimer, can we grant to the ancestors of the ichneumon fly such far-reaching observation and intelligence as really to foresee (not by blind prevision, but through intelligent foresight) the future development of the eggs which she lays in a caterpillar? Are we to suppose that the instinctive action of the young cuckoo, which, the day after it is hatched, will eject all the other occupants of a hedge-accentor's nest,[JE] can have had its origin in lapsed intelligence? If, because of their purposive character, we are to regard such instincts as of intelligent origin, may we not be told that through intelligent design the pike has beset its jaws, palate, and gill-arches with innumerable teeth, all backwardly directed for the purpose of holding its slippery prey; and the eagle has protected its eye with a bony ring of sclerotic plates, like the holder of an optician's watch-glass? If mimicry in form and colour is due to natural selection, why not mimicry in habits and activities? If structures of a wonderfully purposive character have been evolved without the intelligent co-operation of the organisms which possess them, why not some of the highly purposive activities?

And here the disciple of the school of Professor Weismann will echo and extend the question, and will say, "Yes! why not all instinctive activities? You are ready to admit," he will continue, "that many instincts, wonderfully purposive in their nature, are of primary origin, that is due to natural selection; why, then, invoke any other mode of origin? If lapsed intelligence be excluded in these cases, why introduce it at all? Why not admit, what our theory of heredity demands, that[JF] 'all instinct is entirely due to the operation of natural selection, and has its foundation, not upon inherited experiences, but upon the variations of the germ'?"

Professor Weismann's contention needs much more serious consideration than that of Professor Eimer. I think there is force in the à priori argument (as an à priori argument) that since very complex instincts are probably of primary origin, there is no à priori necessity for the introduction of the hypothesis of lapsed intelligence. Let me first illustrate this further.

A certain beetle (Sitaris) lays its eggs at the entrance of the galleries excavated by a kind of bee (Anthophora), each gallery leading to a cell. The young larvæ are hatched as active little insects, with six legs, two long antennæ, and four eyes, very different from the larvæ of other beetles. They emerge from the egg in the autumn, and remain in a sluggish condition till the spring. At that time (in April) the drones of the bee emerge from the pupæ, and as they pass out through the gallery the sitaris larvæ fasten upon them. There they remain till the nuptial flight of the anthophora, when the larva passes from the male to the female bee. Then again they await their chance. The moment the bee lays an egg, the sitaris larva springs upon it. "Even while the poor mother is carefully fastening up her cell, her mortal enemy is beginning to devour her offspring; for the egg of the anthophora serves not only as a raft, but as a repast. The honey, which is enough for either, would be too little for both; and the sitaris, therefore, at its first meal, relieves itself from its only rival. After eight days the egg is consumed, and on the empty shell the sitaris undergoes its first transformation, and makes its appearance in a very different form.... It changes into a white, fleshy grub, so organized as to float on the surface of the honey, with the mouth beneath and the spiracles above the surface.... In this state it remains until the honey is consumed;"[JG] and, after some further metamorphoses, develops into a perfect beetle in August.

Now, it seems to me difficult to understand how, at any stage of this long series of highly adaptive, instinctive activities, lapsed intelligence can have been a factor. And therefore I say, if such a complex series[JH] can have resulted from natural selection and non-intelligent adaptation, I see no à priori reason why any instinct, no matter how complex, should not have had a like origin.

Let us, however, next consider whether Professor Weismann's theory of the origin of instincts necessarily altogether excludes intelligence as a co-operating factor. The essential point on which that theory is absolutely insistent is that what is handed on through inheritance is an innate, and not an individually acquired, character. Now, since intelligent actions are characteristically individual, and performed in special adaptation to special circumstances, it would seem, at first sight, that the intelligent modification of an instinct could not, on Professor Weismann's view, be handed on. Let us consider whether this must be so.

Speaking of ants and bees, Darwin pointed out that their instincts could not possibly have been acquired by inherited habit, since they are performed by neuter insects, that is, by undeveloped females incapable of laying eggs and continuing their race. For a habit to pass into an instinct by inheritance, it is obviously necessary that the organism which performs the habitual actions should be capable of producing offspring by which these actions might be inherited. But in this case the parental forms do not possess these instincts, while the neuter insects which do possess them are sterile.