Behavior of the Lower Organisms

In those animals whose positive reactions are precisely defined and localized, there is, of course, the same evidence that the impulse to change of behavior comes from within and is due to lack or hindrance of the physiological processes, that we find elsewhere. If the metabolic processes lack material for proper action, the medusa or sea anemone changes its behavior and moves about, even though there is nothing present to which it can react positively. When some object is reached, whether there shall be a positive reaction or not depends again on the state of the metabolic processes. If their state is bad, the animal reacts positively to almost anything; if fair, the animal reacts positively to substances that will improve them ; if they are in a completely satisfactory condition, the animal does not react positively even to good food.

Thus with all conditions absolutely favorable there will be no reaction, either positive or negative. At the boundary between favorable and unfavorable conditions, the animal moves in such a way as to retain the favorable conditions. This is primitively due to selection from varied movements — all movement leading to less favorable conditions being changed. The "negative reactions" thus seem to furnish in a certain sense the primitive building stones from which the derived positive reactions are constructed. By development of the power of precise localization of reactions, the derivation of the positive reaction in this manner is in higher animals obscured. The fundamental fact for both positive and negative reactions is that interference with the physiological processes of the organism causes a change of behavior.

We have considered in the three foregoing chapters, first the determining factors of movements, and second the movements themselves. Let us now attempt to put together the most important points in both, so as to reach a general characterization of behavior. The three most significant features of behavior appear to be (1) the determination of the nature of reactions by the relation of external conditions to the internal physiological processes, and particularly the general principle that interference with these processes causes a change in behavior; (2) reaction by varied or overproduced movements, with selection from the varied conditions resulting from these movements — or, in brief, reaction by selection of overproduced movements; (3) the law of the readier resolution of physiological states after repetition. The first of these phenomena produces the regulatory character of behavior. The second and third furnish the mainsprings for the development of behavior, the second being constructive, the third conservative.

The activity of organisms we found to be spontaneous, in the sense that it is due to internal energy, which may be set in operation and even changed in its action without present external stimuli. In reactions this energy is merely released by present external stimuli. What form the activity shall take is limited by the action system, and within these limits is determined by the physiological state of the organism. Physiological states depend on many factors. The two primary classes of states depend on whether the internal life processes are proceeding uninterruptedly in the usual way. Interference with these processes produces a physiological state of a certain character ("negative"), while release from interference or assistance to those processes produces a different state ("positive"). Within or beside these contrasted primary classes, many subsidiary variations of physiological condition are possible, each with its corresponding method of behavior ; at least five of these have been distinguished in a unicellular organism. Any change, external or internal, may modify the physiological state, and hence the behavior.

The effects of external agents depends largely on their relation to the normal course of the life processes — whether aiding or interfering, or neither. A primary fact is that interference with the life processes produces progressive changes in physiological state, inducing repeated changes in behavior. This is in itself regulatory, tending to relieve the interference, whether due to internal or external causes; it is a process of finding a reaction fitted to produce a more favorable condition. When through such changes a fitting reaction is found, the changes in physiological state and hence of behavior cease, since there is no further cause

for change. In the same way a fitting reaction to a beneficial change, or one releasing from interference, may be found. This fitting reaction then tends to be preserved, by the law of the resolution of physiological states, in accordance with which the physiological state inducing this reaction is reached more readily after repetition. Thus the production of varied movements by stimulation is the progressive factor in behavior, while the law of the resolution of physiological states is the conservative factor, tending to retain fitting reactions once attained.

Through the law of the resolution of physiological states behavior tends to pass from the pure "trial" condition to a more defined state. The operation of this law tends to produce reactions precisely localized with reference to the position of the stimulating agent ; increased appropriate reaction to the first weak effects of injurious or beneficial stimuli ; and appropriate reactions to representative stimuli, according as they are followed by injurious or beneficial stimuli. In higher organisms such defining of the reactions has gone far ; much of the behavior consists of derived reactions. There are in such organisms doubtless other factors producing derived reactions, besides the law just mentioned. These are treated in our chapter on the "Development of Behavior."

Thus through the production of varied movements by stimulation the organism finds the best method of behavior, and through the law of the resolution of physiological states it tends to retain this method as long as it is the best method. Through the same process it of course tends to lose this method when it is no longer adapted to the conditions. Thus behavior is regulatory in essential character; it is the process by which the organism tends to find conditions favorable to its life processes and to retain them, and it contains within itself the conditions for its own more efficient development.

It is not the primary purpose of the present work to treat the problems of development, but rather to give an analysis of behavior as we now find it. But the results of this analysis furnish a certain amount of evidence as to how development may have occurred; this it will be well to set forth briefly. We shall consider first the development of behavior in the individual, then its development in the race. In unicellular organisms the first, perhaps, includes the second.

The primary facts for development in behavior are two principles to which our analysis of the chief factors in behavior have led us. One of these is that behavior is based fundamentally on the selection of varied movements. The other is the law in accordance with which the resolution of one physiological state into another becomes readier and more rapid through repetition. In making use of the law of the readier resolution of physiological states after repetition in the study of development, it needs to be kept in mind that this law has been rigidly demonstrated for the lower organisms only in scattered instances. It has been shown to be valid in certain unicellular organisms, but in these cases it has not been shown that the modifications induced are lasting, as must be the case if this law plays a part in the development of behavior. In the lowest metazoa the law has likewise been demonstrated only for a few cases. In the flatworm and the Crustacea we find the law clearly exhibited in the form that is necessary in order that it may play a part in the permanent modification of behavior.

On the other hand, the fact that the law remains undemonstrated for many of the lowest organisms by no means indicates that it is not here valid. We lack proper experiments to show whether it exists or not. It is exceedingly difficult to carry out experiments that shall actually test this matter in the lowest animals. The view that this law is universally valid in organic behavior is thoroughly consistent with all that we know of the behavior of lower organisms, and the fact that it has actually been demonstrated in certain cases favorable for experimentation in unicellular organisms raises a presumption of its general validity. The

following discussion of development is based on the assumption that the law is one of general validity. It must be kept in mind that this is partly an assumption, but the probability that this will be found true is such that the relation of development to the law is worth setting forth. There is no other need greater in the study of animal behavior than that of a thorough investigation of the validity of this law in the lower organisms. The question in which we are here interested is then the following : How can behavior develop ? That is, how can it change so as to become more effective — more regulatory ?

(1) The behavior of any organism may become more effective through an increased tendency for the first weak effects of injurious or beneficial agents to cause the appropriate reaction ; in other words, through increased delicacy of perception and discrimination on the part of the organism. Such a change would be brought about through the law of the readier resolution of physiological states after repetition. When the organism is subjected to a slight stimulus, this changes its physiological state, though perhaps not sufficiently to cause a reaction. Such a slight stimulus would be produced by a very weak solution of a chemical, or by a slight increase in temperature. Now, suppose that this weak stimulus, causing no reaction, is regularly followed by a stronger one, as would be the case if the weak chemical or slight warmth were the outer boundary of a strong chemical solution, or of a region of high temperature toward which the organism is moving. This stronger stimulus would produce an intense physiological state, corresponding to a marked negative reaction. That is, the first (weak) physiological state is regularly resolved by the action of the stimulating agent into the second (intense) one, inducing reaction. In time the first state would come to resolve itself into the second one even before the intense stimulus had come into action. As a result, the organism would react now to the weak stimulus, as it had before reacted only to the strong one. It would thus be prevented from entering the region of the chemical or the heat, even before any injury had arisen.

(2) In the same way the organism may come to react positively or negatively to a stimulus that is in itself not beneficial nor injurious, but which serves as a sign of a beneficial or injurious agent, because it regularly precedes such an agent. Suppose that a slight decrease in illumination (a shadow), which is of itself indifferent, regularly precedes the approach of an enemy, as happens in the sea urchin. The slight decrease in light induces a certain physiological state, which is so little marked that in itself it produces no reaction. But through the immediately following attack of the enemy, this indifferent physiological state is

regularly resolved into an intense one, corresponding to a strong negative reaction. Then after many repetitions of this process the indifferent state resolves itself at once into the intense one, and the animal reacts at the change in illumination, before the enemy has reached it. This tendency to react to "representative" factors, rather than to those which are in themselves beneficial or injurious, is, of course, immensely developed in higher animals. All positive or negative reactions to things merely seen or heard, which are not directly beneficial or injurious save when brought into direct contact with the organism, are, of course, reactions to such representative stimuli.

It is clear that neither the tendency to react to faint stimuli, nor that to react to "representative" factors will be increased, save as this is required by the environment. If the indifferent stimulus is not followed with some regularity by the powerful one ; that is, if it does not really introduce a powerful agent, then there will be no tendency for the organism to acquire a reaction to this indifferent stimulus, for there will be no regular resolution of the first (faint) physiological change into the second (intense) one. And of course it would be no advantage, but on the co'ntrary a positive disadvantage, for the organism to acquire tins tendency to react to all weak stimuli. If it reacted negatively to every slight change in the environment, its movements would be seriously impeded ; continued locomotion in any one direction would be almost impossible, and its activity would be frittered away in useless and disconnected reactions. The behavior becomes modified, in accordance with the principles above set forth, only as it is to the advantage of the organism that it should be so modified; that is, only as the modification favors the normal current of life activities.

(3) Progress takes place through increase in the complexity and permanence of physiological states, and in the tendency to react to these derived and complex states, instead of to the primitive and simple ones. We may imagine an organism whose physiological state depends entirely on the stimulus now acting upon it, the organism returning completely, as soon as the stimulus ceases, to its original state. Such an organism could react only with relation to the present stimulus, and its reaction to the same stimulus would always be the same. We might even imagine an organism that could change in only one way under the action of stimuli ; its reactions to all stimuli would be the same. Such organisms would represent a purely reflex type of behavior. An advance on this condition would be represented by cases where the physiological state induced by a stimulus endures for a short time, influencing the immediately succeeding reactions, and a further advance when the reaction performed by the organism influences its physiological state, and therefore its later

reactions. Other advances would come in the production of different physiological states according to the different organs or parts of the body stimulated; this condition would naturally arise as structural differentiations were developed in the body. As new organs develop and the body becomes more complex, each part will naturally have physiological states peculiar to itself, and will be acted upon by external stimuli, producing changes in its physiological states. This is evidently the case in such organisms as the sea urchin and sea anemone. These partial physiological states of the different organs will then interact, altering each other and combining to form a general state for the entire organism. All the partial physiological states will be regulated, as in the separate organism, bv their relation to the normal life current of the organ concerned, and further, their combinations will be regulated by their relation to the general life current of the organism. Whatever interferes with this normal life current will be changed, while that which does not interfere must persist. The partial and general physiological states will be subject to the laws of the combination and regulation of physiological states, just as in simple organisms. They will tend to discharge themselves in action, or by resolution into other states, as in the simple organisms. Thus the behavior of the organism must become in time controlled by these physiological states, derived from many sources besides that of the present stimulus. Behavior is gradually emancipated from its bondage to present external conditions, and depends largely upon the past experience and present needs of the organism. This is the condition we find in higher animals, and especially in man.

The various stages set forth above are merely logical divisions, and probably do not correspond in any close way to actual stages in the development of behavior. There seems to be no reason to suppose that an organism ever existed in which the original state is immediately restored on the cessation of a stimulus. This immediate return to the original state is not what we should expect from analogy even with inorganic substances.1 Even in unicellular organisms we find a considerable complication of physiological states, depending on past stimuli, past reactions, localization of the stimulus, and present external conditions, as well doubtless as upon other factors.

Progress along the line just set forth will be brought about by the same factors, whatever they may be, that determine the development 1 With relation to colloids, the substances of which organisms are mainly composed, a high authority in physical chemistry remarks as follows: "Their qualities often depend in the clearest way upon the former history of the colloid, its age, its previous temperature, and the time this continued : in short, on the way it has reached its present condition " (Bredig, 1902, p. 183). The facts of behavior in organisms might be cited as illustrations of this statement.

of complexity in structure. Differentiation of structure and of physiological states must go hand in hand. It is not our province to attempt to account for structural differentiations. The problem is the general problem of evolution. (4) Progress in behavior may take place through increased variety and precision of the movements brought about by stimulation. Certain kinds of movements are much better adapted to relieving an organism from an unfavorable stimulation or securing it a favorable one than are others. This is illustrated by a comparison of the reactions of Amoeba and Paramecium, or of the reaction of Bursaria to heat with that of Paramecium, as set forth on page 305. Owing to the difference in the effectiveness of their movements, if an area containing equal numbers of Paramecia and Bursaria is heated at one end, many of the Bursariae are killed, while all the Paramecia escape.

. New and better adapted methods of movement may be acquired through the selection of varied movements, in conjunction with the law of the resolution of physiological states. Under strong stimulation the organism, as it passes from one physiological state to another, tries successively all the movements of which it is capable. One of these movements (the spiral course, in the case of Bursaria) finally removes the organism from the stimulating agent. This happens every time the organism is stimulated in this manner. The result is that each physiological state is resolved into the succeeding one, until that one is reached in which the organism responds by the effectual movement. After a number of repetitions, this resolution takes place immediately, in accordance with the law that after repeated resolutions of one physiological state into another, this resolution takes place spontaneously and rapidly. Thus the organism responds at once with the effectual movement, and escapes.

In the same way the use of new organs might be acquired. Suppose that an Amoeba sends forth, as sometimes happens, a long, slender pseudopodium, which may vibrate back and forth, like a flagellum. When stimulated, the overproduced movements of the organism, as it passes from one physiological state to another, include the vibration of this pseudopodium. Suppose that by this vibration the Amceba is at once moved away from the stimulating agent — the pseudopodium acting as does the flagellum in Euglena. If this is repeated, the physiological state inducing other movements will always be resolved finally into that inducing this one, and in time this resolution will take place so rapidly that only this movement will come to actuality. The Amoeba will have acquired the habit when stimulated of swimming by means of a flagellum. Thus the behavior of organisms is of such a character as to pro-

vide for its own development. Through the principle of the production of varied movements, and that of the resolution of one physiological state into another, anything that is possible is tried, and anything that turns out to be advantageous to the organism is held and made permanent. Thus through development in accordance with the two principles mentioned, the organism comes to react no longer by trial, — by the overproduction of movements, — but by a single fixed response, appropriate to the occasion. This is, of course, a great advantage, so long as the conditions remain such as to make the response appropriate. Such fixed responses are the general rule in the adult behavior of higher organisms, and are found to a certain extent in all organisms. In the higher organisms we speak of some of these fixed responses as reflexes, tropisms, habits, and instincts. The methods which we have discussed are not the only possibilities for the development of such responses ; other methods we shall take up later.

After the responses of the organism have become fixed, conditions may so change that these responses are no longer appropriate. The organism is then in a less advantageous position than one whose behavior is determined more purely by trial movements. There will be now a tendency for the fixed responses to become broken up and for processes of trial to supplant them, until new fixed responses, appropriate to present conditions, are produced. But in many cases the fixed responses are so firmly established as not to give way save after long experience of their lack of efficiency, and often the organism is destroyed by the new environment, before it has developed appropriate responses by which to preserve itself.

(5) We have thus far considered primarily the methods by which the behavior of a given individual may be modified and made more effective. It needs to be recalled that differences between the behavior of different individuals may appear from other reasons. There are congenital variations among different organisms. Some have naturally a greater delicacy of perception or discrimination than others. Some move more rapidly or in more or less varied ways than others, giving some a more efficient method of reaction without any modification through experience. These congenital variations play a most important part in the question next to be considered.

(6) Our discussion thus far has related to individuals. The further question arises as to how modifications of behavior may arise in the race as a whole. How does it happen that the behavior of the race becomes changed in the same way as that of the individual, so that succeeding generations show the new method of reacting without acquiring it for themselves ? There seems to be no question but that the power of new individuals to react in certain ways without preliminary trial has been much overestimated. In most organisms there is in the early stages of development a continued process of trial, through which the habits become established. On the other hand, there is no doubt that individuals do appear with certain ways of reacting which most of their early ancestors did not at the beginning have. The question as to how this happens, therefore, presses for an answer.

The answer formerly given was, that the acquirements of the parent are directly inherited by the offspring. The parent having come to react in a certain way, the condition of the system inducing this reaction is passed on to posterity. In the unicellular organisms there seems to be nothing in the way of this inheritance by the offspring of the reaction methods acquired by the parent. There is no distinction between germ cells and body cells in these organisms; all acquirements pertain to the reproductive cells. Through reproduction by division the offspring are the parents, merely divided, and there is no evident reason why they should not retain the characteristics of the parents, however these characteristics were attained. If this is the real state of the case, then in unicellular organisms the life of the race is a direct continuation of the life of the individuals, and any acquirements made by the individuals are preserved to the race.

But in multicellular organisms the facts show that in the immense majority of cases the inheritance of the acquirements of the parents by the offspring does not occur. We know that we do not start with the education acquired by our parents, but must begin at the bottom, and acquire both knowledge and wisdom of action. In other words, we know that we fail to inherit directly the more efficient methods of reaction acquired through experience by our parents, in at least nine hundred and ninety-nine cases out of a thousand. Moreover, the theoretical difficulties in the way of such inheritance are great, and no demonstrative evidence seems to exist that it ever occurs. Thus we are certain that in most cases it does not take place, and must doubt whether it is possible.

If we give up, as most students of heredity do, the inheritance of acquired characters, the alternative explanation for progress in the race is by natural selection of congenital variations. The theory of natural selection may be stated briefly as follows : Organisms vary in many ways, through variations affecting the germ cells. Among these variations are some that help the organism, making it more efficient in escaping enemies or in obtaining food. These organisms, therefore, survive, while those without these helpful variations are killed. The surviving organisms transmit their helpful congenital variations to their offspring,