under their biological aspect not less important than the former, are under their psychological aspect of perhaps even greater importance. For the conditions of actual struggle are not those under which mental development could most easily be furthered, though they are those in which it is most effectually tested. Hence, the more intelligent animals pass through a period during which they are more or less shielded from the incidence of natural selection by their parents, and this is the period of play and of psychological education. And the tendency to play is so far organic, in that it is dependent on inherited instinctive propensities, and so far psychological in that it is accompanied by a felt want, which constitutes a conative impulse finding its appropriate end in the consciousness of satisfaction. But play-if we accept the term as the groupname for all those modes of behaviour which fall under our second class, those of indirect biological value-does not cease with the period of youth; it occupies all the intervals in the more serious business of animal life. And no discussion of animal behaviour can be adequate which does not assign to this class its due place, alike in biological and in psychological evolution.

The whole value of experience lies in the linkage and coalescence of the data afforded to consciousness. It is true that an inherited nervous system supplies the organic conditions of that physiological linkage and functional coalescence of which experience is the psychological expression. It is true that this physical integration secures a ready-made grouping of the conscious data which are the concomitants of orderly molecular changes in the brain or analogous sensorium. Still, it also remains true that the value of experience lies in the further linkage and coalescence that is acquired by the individual in the course of what we may fitly call its education. Every step in this education gets its psychological sanction through the satisfaction it affords in consciousness; and the time of acquisition is not during the stress of examination in the actual struggle for existence, but rather in the youthful period and in the subsequent intervals of preparation and practice, during the play-time of animal life.

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The examination analogy-if, indeed, it may not be rightly regarded as something more than an analogy-may be pressed a little further as a means of fixing our attention on two points which are worthy of consideration. The first is that, in the preparation for the examination, specific practice as much of it is, cramming is not the system exemplified by the higher animals. A good all-round education in the acquisition of conscious situations more or less coalescent into a unified system of experience, and in their effective utilization without unnecessary delay and bungling along more or less converging lines of practical behaviour; this is what secures a pass in survival, especially where the circumstances of life have reached a considerable degree of complexity. The instinctive act, with its relatively definite response to a question which is almost certain to be set to every candidate for survival, is that which is the analogue in behaviour to the result of a system of cram. Organic nature does employ this system in the lower classes of her school; definite responses are ground into merely instinctive types generation after generation, and the right answers are given, automatically and unintelligently, whenever the oft-recurrent questions are set. But this will not do when the questions require the exercise of intelligence, when they are of the nature of problems, with just those delicate but not unimportant shades of difference which baffle the candidate who has been drilled in a merely mechanical fashion. Hence the cramming of instinct does not suffice for animals whose environment presents problems of greater variety and greater complexity. Intelligence is required to meet the particular combinations as they arise. The greyhound, which is loosed on a hare, has never seen that hare run in exactly that way over that special tract of country. But he has been trained in such situations, and is thus prepared to meet the special problem in its details as they present themselves in the light of the experience he has gained of other like problems. And his skill in pursuit has not only been gained through education in coursing. In a thousand ways, as puppy and dog, he has learnt how to use well those sinewy limbs. The training of

his whole life is brought to bear on the question immediately before him.

The general bearing of these facts is obvious. Play, as a means of animal education, is varied, and has for its end allround training of the animal mind in its sphere of operation. Although there are some specific propensities, certain observable trends of behaviour, as in hunting-play, courtship-play, and the like, we must not expect, nor do we find, anything like stereotyped definiteness of conative activity. We find that freedom and elasticity in animal education which is, perhaps, more often advocated than carried into practice in human education.

The second point arising out of the examination analogy is, that its range determines the level of preparation therefor. It is, for animals, a practical examination, not a theoretical. Not a single question is set demanding an explanation. The problems are such as can be solved by intelligence, not such as require the exercise of reason, as we have used the term in foregoing pages. These higher problems are only set when the sixth form is reached, and there is no conclusive evidence that any animals get into the sixth. This, however, is entirely a question of evidence, and many of us will be glad to welcome them there, if proved ability to deal reflectively with ideational questions justifies their promotion.

If any of them do belong to this form, they have probably got there through play. For in the stress of the actual examination there is not much time for reflection. Or perhaps we may rather say that, not in actual struggle, and not in active preparation for it in play-time, but in intervals of leisure between both, when the animal lies quietly turning over in his mind we know not what, will experience be reviewed, and generalizations drawn as to the why of events in this strange world. Probably the animal accepts things as they are, and does not trouble about their explanation. But it may not be so. At any rate, if animals lack the means of descriptive inter-communication, and have no words as concrete pegs on which to hang abstract ideas, their explanations

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cannot be carried far. Theories without the power of disputation would be a poor solace in leisure moments.

One more point may be noticed with regard to the psychological aspect of the evolution of behaviour-the reciprocal action of intelligence. It is the intelligence of others that introduces so much variety and complexity into the environment. Hunters and hunted, combatants, rivals, mate and mate, enemies or companions in their varied aspects, introduce through their intelligence complications which only intelligence can meet. And, as intelligence begets intelligence, so do emotional attitudes beget answering emotional states. Psychological evolution translated into practical behaviour gives rise to situations of reciprocal complexity. This point of view is, however, so familiar, that nothing need be said in its further elucidation. The behaviour of any given animal does not stand alone, but is closely related with the behaviour of others. Among social animals the relationships are peculiarly close, and it is among them that the psychological aspect of behaviour reaches its highest expression.

Under the head of organic behaviour, in the widest acceptation of the term, fall the whole of physiology, the whole of embryological development, nay, more, the whole of organic evolution; while mental evolution, in all its stages, may be regarded as the psychological aspect of that which, from the physiological aspect, is the evolution of nervous systems. Life itself is the behaviour of a particular kind of substance which is found more or less abundantly under natural conditions. No other known substance behaves in this way, and so ignorant are we as to the conditions of its natural origin, that it is useless to guess at a scientific explanation. And even if we knew all the antecedents and conditions of its origin we should be no nearer a comprehension of why protoplasm has the peculiar properties which we find it to possess. That is a question to which science can give no answer. Who knows

why a certain compound of oxygen and hydrogen in certain proportions has the properties of that which we call water?

Let us note the distinction between saying, as we said above, that life is the behaviour of protoplasm, and asserting that life is the cause of this behaviour. The one is a scientific statement of observed fact, the other an explanation of the fact in metaphysical terms, a reference of the fact to its underlying cause. So long as we quite clearly understand that we are talking the language of metaphysics, we may speak of life as a cause of organic behaviour; but let us be careful to remember that the statement has no more value for science than the assertion that aqueosity is the cause of the behaviour of water.

Leaving on one side, then, the natural origin of protoplasm, the conditions of which are unknown, we find that, as a matter of observation, every bit of living substance, the history of which has been traced, is a fragment detached from some other bit which behaved in the same way. This is the basal fact of the continuity of organic evolution. But such a detached fragment has the property of increasing by taking up from the environment more of those elementary materials from which it is itself compounded in subtle synthesis. Nay, further, every fragment of which we know the history is found to increase in such a way as to reach, in form, structure, and idiosyncracies of behaviour, the likeness of the organismplant or animal-from which it was derived. In the higher plants and animals the separated fragments or cells are the ova and sperms, or their equivalents, which unite, with fusion or coalescence of their nuclear matter, and thus give rise to a new individual in the course of embryological development.

Now, as we have already seen, much modern biological discussion centres round the question whether the detached reproductive fragment, ovum or sperm as the case may be, is derived from the whole body of the parent, by what Darwin termed pangenesis or in some other way, or only from stance set apart in development for this end. provisionally accepted the hypothesis that it

germinal subAnd we have is the direct