In laying stress on the biological value of certain modes of behaviour which we thus call play, a value which lies in the practice and preparation they afford for life’s more earnest work, Professor Groos deserves our hearty thanks. Nor need our thanks be less hearty if we find that he has in some degree been anticipated by Darwin; for he has elaborated with systematic care what Darwin suggested incidentally. “Nothing is more common,” said Darwin,[135] “than for animals to take pleasure in practising whatever instinct they follow at other times for some real good. How often do we see birds which fly easily, gliding and sailing through the air, obviously for pleasure! The cat plays with the captured mouse, and the cormorant with the captured fish. The weaver bird, when confined in a cage, amuses itself by neatly weaving blades of grass between the wires of its cage. Birds which habitually fight during the breeding season are generally ready to fight at all times; and the males of the capercailzie sometimes hold their Balzen, or leks, at the usual place of assemblage during the autumn. Hence it is not at all surprising that male birds should continue singing for their own amusement after the season of courtship is over.”
In the behaviour of courtship we have what is essentially part of the serious business of animal life. And in including it under the heading of “Love Plays,” Professor Groos may seem to be forgetful of his own definition of play. He is, however, too clear a thinker not to see, and too honest an exponent not to say, that much of the emotional behaviour commonly regarded as courtship falls outside his main thesis “in being, strictly speaking, not mere practice preparatory to the exercise of an instinct, but rather its actual working.”[136] But behaviour of a somewhat similar kind is seen in young animals before the time of mating has arrived, and is exemplified both in young and adults under circumstances different from those which distinguish what we may term the pairing situation. This, at any rate, may be regarded as a form of experimentation and practice in the arts of courtship. On different grounds does Professor Groos attempt to justify the inclusion of actual courtship under the head of play. For it may also, he thinks, even at the time of its serious exercise, be to some extent artful, involving “make believe,” and therefore playful in a somewhat different and more subtle sense; but a brief reference to “make believe” we may reserve for our next section.
There can be no question that special modes of behaviour often characterize the pairing situation, and that these not only exemplify an instinctive tendency, but from their constancy and relative definiteness constitute types of instinctive behaviour. They would form parts of any definition of a species founded not on structure but on behaviour. And if animals have feelings and emotions at all—if they are not Cartesian automata, which merely seem to be guided in their actions by consciousness—there can be but little question that the behaviour which characterizes the sexual situation is unusually charged with feeling-tone, and accompanied by all those adjuncts which distinguish an emotional state, broadly considered. This matter is of no little importance in our interpretation of the phenomena described as courtship. Do the accompanying feeling-tone and the state of emotional exaltation influence the behaviour, or would it run a similar course in the absence of any such accompaniments? If, as we can scarcely doubt, the consciousness attending the situation does profoundly influence the behaviour, the further question arises—Is this influence mainly the result of the presence and behaviour of an individual of the opposite sex? To this, again, we must answer that, so far as we can learn by observation, behaviour unquestionably is determined by such influence in the serious business of courtship. And then the further question arises—Is it a matter of indifference what the appearance and behaviour of the individual of the opposite sex may be? Are A., B., C., and the rest of the male alphabet, precisely alike in stimulating in a similar manner, and to a similar degree, the sexual impulse of the female? If we admit any differential influence, and if this influence takes effect in the sexual union to which courtship is preparatory, we so far admit the efficacy of that which Darwin termed sexual selection.
Let us, however, before proceeding with general considerations, present one or two examples of the facts which observation has furnished with regard to specialized modes of behaviour at the time of pairing. Speaking of American night-hawks, Audubon says, “Their manner of flying is a good deal modified at the love season. The male employs the most wonderful evolutions to give expression to his feelings, conducting them with the greatest rapidity and agility in sight of his chosen mate, or to put to rout a rival. He often rises to a height of a hundred metres and more, and his cries become louder and louder as he mounts; then he plunges downward with a slanting direction, with wings half open, and so rapidly that it seems inevitable that he should be dashed to pieces on the ground. But at the right moment, sometimes when only a few inches from it, he spreads his wings and tail, and, turning, soars upward once more.”[137] Mr. Strange, quoted by Darwin[138] says of the satin bower-bird, “at times the male will chase the female all over the aviary, then go to the bower, pick up a gay feather or a large leaf, utter a curious kind of note, set all his feathers erect, run round the bower and become so excited that his eyes appear ready to start from his head; he continues opening first one wing, and then the other, uttering a low, whistling note, and, like the domestic cock, seems to be picking up something from the ground, until at last the female goes quietly towards him.”
Darwin describes how, in the Argus pheasant,[139] “the immensely developed secondary wing-feathers are confined to the male, and each is ornamented with a row of from twenty to twenty-three ocelli, each above an inch in diameter. These beautiful ornaments are hidden until the male shows himself before the female. He then erects his tail, and expands his wing-feathers into a great, almost upright, circular fan or shield, which is carried in front of the body. The ocelli are so shaded that, as the Duke of Argyll remarks, they stand out like balls lying loosely within sockets. But when I looked at a specimen in the British Museum, which is mounted with the wings expanded and trailing downward, I was,” adds Darwin, “greatly disappointed, for the ocelli appeared flat or even concave. Mr. Gould, however, soon made the case clear to me, for he held the feathers erect, in the position in which they would naturally be displayed, and now, from the light shining on them from above, each ocellus at once resembled the ornament called a ball and socket.” The primary wing-feathers are scarcely, if at all, inferior in beauty to the secondaries, though the markings are quite different, the chief ornament being a space parallel to the dark-blue shaft, which in outline forms a perfect second feather lying within the true feather. “Now the secondary and primary wing-feathers are not at all displayed, and the ball and socket ornaments are not exhibited in full perfection, until the male assumes the attitude of courtship.”
It is unnecessary to describe the song of birds which is generally, but not always, at its best during the period of pairing. Bechstein, who kept birds during his whole life, and studied them with care, asserts that “the female canary always chooses the best singer, and that in a state of nature the female finch selects that male out of a hundred whose notes please her most.”[140]
Thus we are led back to sexual selection. If we are satisfied that the males of certain species do as a matter of fact behave in specific and distinguishable ways at the breeding season, and in presence of their would-be mates, the question is, What, if any, is the biological value of such behaviour? What has fostered and guided it in the course of its evolution? From the case of the Argus pheasant, which is only a sample of the large class of cases in which the male has special adornments, we see that the behaviour has often direct relation to the display of such plumage, or, in some apes, of coloured surfaces, so that behaviour and ornamentation must be taken together. The essence of Darwin’s contention is, that the adornments and behaviour give rise to a situation through which the female is stimulated or excited to accept the male; that the male in which they are best developed gives rise to the most effective situation, produces most excitement, and therefore has the best chance of acceptance, being “unconsciously preferred;”[141] and that he thus begets offspring which inherit his adornments and modes of behaviour, such inheritance being, however, confined to the males. Thus sexual selection takes effect through preferential mating, whereby certain hereditary traits are transmitted and become racial characteristics. And this is brought about through an appeal to consciousness, and seems to involve choice—generally that of the female.
Now, as I have elsewhere urged,[142] the hypothesis of sexual selection has often been placed in a false light by the introduction of the unnecessary supposition that the hen bird, for example, must possess a standard or ideal of æsthetic value, and that she selects that singer which comes nearest to her conception of what a songster should be. Darwin occasionally expressed himself unguardedly in the matter; he says, for example, that the female appreciates the display of the male, and places to her credit a taste for the beautiful.[143] But he also distinctly states that “it is not probable that she consciously deliberates; she is most excited or attracted by the most beautiful, or melodious, or gallant males.”[144] This is all that is really necessary for the theory of sexual selection. The hen accepts that mate which by his song or otherwise excites in sufficient degree the pairing impulse; if others fail to excite this impulse, they are not accepted. Even Mr. A. R. Wallace, who rejects the theory save in a very subordinate form, says[145] that “it may be admitted, as highly probable, that the female is pleased or excited by the display,” and speaks[146] of a possible choice of “the most vigorous, defiant, and mettlesome male,” giving, moreover,[147] several telling examples of preferential mating. Stripped of all its unnecessary æsthetic surplusage, at any rate so far as this implies an æsthetic ideal, or æsthetic motive, the hypothesis of sexual selection suggests that the accepted mate is the one which adequately evokes the pairing impulse.
Here Dr. Groos makes an interesting and important contribution to the subject. He lays stress on the coyness and reluctance of the female, and illustrates it by examples derived from observation. “Thus the female cuckoo answers the call of her mate with an alluring laugh that excites him to the utmost, but it is long before she gives herself up to him. A mad chase through tree-tops ensues, during which she constantly incites him with that mocking call, till the poor fellow is fairly driven crazy. The female kingfisher often torments her devoted lover for half a day, coming and calling him, and then taking to flight. But she never lets him out of her sight the while, looking back as she flies and measuring her speed, and wheeling back when he suddenly gives up the pursuit. The bower-bird leads her mate a chase up and down their skilfully built pleasure-house, and many other birds behave in a similar way. The male must exercise all his arts before her reluctance is overcome. She leads him on from limb to limb, from tree to tree, until it seems that the tantalizing change from allurement to resistance must include an element of mischievous playfulness.”[148]