Behavior of the Lower Organisms

so that in time an entire race may show the characteristics which first arose as accidental variations along with many other useless ones. A great objection to this theory has been that it deals merely with chance variations in all directions, so that progress along a definite line, it is said, could never be brought about through it. The race progresses just as the individuals do; what is first acquired by the individual is later acquired by the race, as if the law of progress were the same in the two cases. This, it is held, could not be brought about through the selection of chance variations in all directions.

In recent years a most successful attempt has been made by J. Mark Baldwin (1902) and others to show that this objection is not a valid one; that the action of natural selection on characters playing a part in the behavior would, in fact, be guided by laws similar to or identical with those controlling the progress of the individual. To this guidance the name organic selection has been given. Organic selection would then account for the progress of the race in a continuous manner and in a definite direction. We shall examine briefly, from this point of view, the action of natural selection on behavior in the lower organisms.

Observation and experiment show that there exist such variations in the behavior of lower organisms as would under certain circumstances give opportunity for the action of natural selection. If into an area containing Paramecia a drop of a 10 per cent sugar solution is introduced, most of the animals enter it and are killed, but a few react negatively on coming in contact with it, and escape. If such solutions were a constant feature of the environment, it seems probable that in time there would be produced through selection a race of Paramecia that would always react negatively to them, and would, therefore, not be endangered by their existence. Similar differences exist among different individuals as to sensitiveness to other chemicals, to heat, and to electricity, as we have seen in previous pages. There is thus undoubtedly an opportunity for the action of natural selection to produce a race of organisms more sensitive to weak stimuli than is the average at present, if the environment should require it. But if the environment does not require it, the action of natural selection, like that of individual accommodation, will not bring it about. By either method only that is preserved which is useful.

There is likewise clearly an opportunity for natural selection to produce a race showing increased precision and adaptiveness in the movements brought about by stimulation. As we have seen on page 305, the reactions of Paramecium to heat are so much more effective than those of Bursaria that if locally heated regions were part of the usual environment of the two organisms, the Bursaria? would, for the greater part, soon be killed, while the Paramecia would not suffer. The latter would, therefore, be selected, as compared with the former. But thereexist variations of reaction even among individuals of the same species. Some specimens of Bursaria when stimulated by heat show a greater inclination to swim freely, revolving on the long axis, than do the majority, that sink quickly to the bottom and cease to revolve. The former are saved from the heat, while the latter are killed. In time there might thus be developed a race of Bursarias that were as well protected by their behavior from the action of heat as are Paramecia.

What are the characteristics that would be preserved by natural selection? First it seems clear that under usual conditions the regulative power would tend to be preserved. So long as the environment is a changing one, those individuals that can alter their behavior to lit the new conditions would live, while any that cannot do so will be killed, so that any variation in the direction of less regulative power will be cut off. But under quite uniform conditions there might be no advantage in this regulative power, and no selection based upon it.

Second, those variations will be preserved that are in line with the general tendency of the behavior. In other words, those variations will persist that tend in the same direction as the adaptation of the individuals, due to selection of overproduced movements and the law of the resolution of physiological states. This will be made clear by an illustration. Most ciliate infusoria may swim freely through the water, may creep along surfaces, may exude mucus to form a cyst, and may burrow about in the debris at the bottom of the water. Some show one habit in a more marked way, others another. Let us suppose a ciliate infusorian with a cylindrical body covered uniformly with cilia, that may behave in all these ways. It responds to stimulation by trial of the different reactions which it has at command, continuing, in accordance with the principle of the resolution of physiological states, that reaction which proves successful. Suppose that a number of the individuals come thus to react habitually in the first of the four ways mentioned above, others in the second, others in the third, and still others in the fourth. All these different methods have advantages for meeting unfavorable conditions, and all are found as a prevailing reaction in different ciliates.

We have then four groups of ciliate organisms, all alike structurally, but with different habits. How will natural selection act on these? (i) In the first group, that swim freely through the water, like Paramecium, all variations that favor quickness of reaction, rapidity of movement, and precision of direction will be advantageous, and the individuals possessing them will tend to be selected. Specimens with body ill-shaped for rapid movement, with cilia weak or unequally distributed,

or with awkward methods of moving, will be killed by their inability to escape with sufficient rapidity from powerful agents. There will thus .be a tendency to develop a fishlike form, adapted for rapid movements through the water; close-set, uniform cilia, and a tendency to revolve on the long axis ; in other words, such characteristics as we find in Paramecium. (2) In the second group, which reacts, like Oxytricha, by running along the bottom, variations of an entirely different character will be advantageous. The original cylindrical form can bring but few of its cilia against a surface, and presents much resistance to the water. Variations in the direction of a flat form, bringing many cilia against the surface, and presenting little resistance to the water as it runs along, will be advantageous, and individuals with such variations will be selected. The cilia on the surface kept against the bottom will be the allimportant ones, so variations in the direction of increased size, strength, and rapidity of these cilia will be preserved ; they will develop into "cirri" and other leglike structures. The cilia on the upper side of the body will be not merely useless, but a hindrance; hence they will tend to be lost. The tendency to revolve on the long axis will be injurious and will likewise tend to disappear by selection of those that do not thus revolve. In this way, under the action of natural selection, an organism will be developed having totally different characteristics from the organisms of the first set, that react by swimming freely. It will naturally approach the characteristics shown by Stylonychia, rather than those of Paramecium.

(3) On the third organism, which reacts to intense agents by secreting a layer of mucus about itself, natural selection will act in a still different manner. There will be no tendency to select rapidly moving individuals, nor those having larger or more numerous cilia, nor those having cilia distributed in any special way; all these characteristics will indeed be disadvantageous. Spiral swimming will not be developed. Those organisms that produce a thicker layer of mucus, of a more resistant character, and do this the more rapidly, will be selected.

(4) The fourth organism, which habitually reacts by burrowing into the detritus at the bottom of the water, will be acted upon by natural selection in a still different way. Only those characteristics which aid the burrowing will be useful and therefore selected. There will be no tendency to produce a swiftly swimming organism, nor one adapted to running along the bottom, nor one secreting a thick and resistant layer of mucus. To sum up, it appears that only those variations are of advantage that are used, and only such variations can be preserved by the action

of natural selection. Only such characteristics can be selected as are in line with the efforts of the organism. A variation which might be of inestimable advantage to an organism that reacts by swimming would be entirely lost on one that burrows in the earth. The organism determines by its own actions the direction of its development under the action of natural selection. When it adopts a certain line of behavior, it decides to a large degree the future career of the race. Development through the action of natural selection must then follow as definite a trend as does the behavior of the individual and indeed the same trend, for it is guided by this behavior. Individual selection guides natural selection.

Individual selection, with its production of definite adaptive reactions, is due, of course, to selection from varied movements, later fixed by the law of the readier resolution of physiological states.1 With this in mind, we may express what we have just brought out as follows : In- dividual selection (intelligence) and natural selection are merely different methods of selecting adaptive ways of reacting. The former selects the adaptive response from among diverse reactions of the same individual; while natural selection selects the adaptive response from among diverse reactions of different individuals.

This may be illustrated as follows: Let us suppose an organism whose action system includes the different acts i, 2, 3, 4, 5, 6, 7, 8, 9. When the physiological processes of this animal are interfered with by external agents, it tends to run through these nine reactions, in the order given above — as Stentor runs through its four or five reactions. Suppose that under a certain frequently recurring injurious condition the reaction 7 is the adaptive one, relieving the interference with the physiological processes. The organism runs through the series to 7, then stops (since the cause for further reaction has ceased). It now retains this reaction as the immediate response to the given condition, through the law of the readier resolution of physiological states. Many of the individuals are killed before 7 is reached, but after this adaptive reaction has become fixed, no others are killed. The young of these individuals must, however, begin at the beginning of the series, so that many will be destroyed.

Let us suppose that in another group there are, among many different individuals, congenital variations in the order in which the nine responses are given. Some respond by the series 2, 3, 7, 1, 4, 5, 6, 8, 9. These reach the adaptive reaction 7 sooner than do those following the usual order, hence fewer are killed by the injurious condition. Others react in the order 7, 4, 3, 5, 1, 2, 6, 8, 9. The first reaction is here the 1 This is the process known as intelligence, in higher animals. See Chapter XX.

adaptive one. Hence the series goes no farther (since the cause for reaction ceases at once), and these organisms are not killed at all by the injurious condition. They are thus selected, as compared with those reacting in the usual way, and their method of reacting, being congenital, is inherited by posterity. In the course of time all the remaining individuals of this group will respond at once, like those of the previous group, by the reaction 7.

Thus individual selection and natural selection necessarily work to the same result. One selects from among the different acts of the same individual, the other from among those of different individuals. The thing selected is the same in each case, — namely, the adaptive reaction. If there exist at the same time the power of individual modification and the variations on which natural selection acts, then under uniform conditions the latter will be more effective, since it results in immediate response by the adaptive reaction, while the former requires that every new individual should go through the trial series, with its attendant dangers of destruction. If the conditions are very severe, in time only the individuals which have inherited the immediate adaptive response will survive. Thus, through the action of natural selection these organisms will have an inborn tendency to react directly in an adaptive way, whereas in previous generations most of the individuals of the race acted in this manner only as a result of individual modification through experience.

Furthermore, it may be pointed out that in the course of time an organism which had adopted some special type of behavior, as burrowing, would become quite unadapted to other behavior, as running along the bottom or swimming through the water. It develops structures, under the influence of its adaptive behavior, that make it difficult or perhaps impossible for the organism to react in any other way than by burrowing. After a time, then, it will lose all tendency to react in other ways, because it cannot react in other ways, owing to the structural changes it has undergone. In most cases the specialization will not go so far as this, and the organism will retain the power of attempting other methods of reaction; that is, of performing other movements. But these movements will be ineffectual, because the structures of the organism are not adapted to their performance. They will therefore not relieve the organism from stimuli ; hence they will be quickly exchanged for the movements which are effective. Thereafter the organism will always react by these movements on which its structure is based. If these first few ineffectual movements are not observed, it will appear that the organism has been rigidly limited from the beginning to this one type of behavior. Apparently there exist few if any organisms

which do not show, in their younger stages at least, a few such ineffectual movements. Baldwin suggests that the same process may go farther than this, in the following way: After the development, under the influence of a certain reaction method, of structures fitted to carry out that method, another congenital variation may occur, by which energy will be discharged directly into this apparatus, in the way necessary for performing the accustomed reaction, without any previous trial. It is urged that after the apparatus has been developed, the further variation required would probably be slight and not unlikely to occur. The organisms having this variation must react more readily and rapidly than those in which a trial is required, hence they might be selected. Thus in time in the entire race the reaction would be limited to this particular method. There seems to be no theoretical difficulty as to the occurrence of such a variation ; if it occurs, development would doubtless take place in the way set forth, provided the environment remain sufficiently constant. But perhaps there would be little difference in reality between the behavior of such an organism, and one which had merely developed such structures as to make difficult any kind of reaction save one. The latter would still reserve the capability of developing other reactions, under changed circumstances, while the former would not.

The guidance of natural selection by the actions of the individuals that we have illustrated above, is what has been called "organic selection." The latter is evidently merely an exposition of how natural selection acts, not anything additional to natural selection, or differing from it in principle. For a general discussion of the questions which it involves, reference should be made to J. Mark Baldwin's "Development and Evolution." Is natural selection, thus guided by individual accommodation, sufficient to account for the progress of the race in behavior? It is clear that natural selection cannot account for the origin of anything; only that can be selected which already exists. All the potency of behavior and of everything else that exists must lie in the laws of matter and energy, — physical and chemical, and possibly vital laws. Whatever the part assigned to natural selection, the superlative importance of these laws remains ; they must continue the chief field for scientific investigation. All that natural selection is called upon to explain is the fact that at a given time such and such particular manifestations of these general laws exist, rather than certain other manifestations. In the field of behavior it is called to explain only the fact that this particular organism now behaves in this particular way, rather than in some other one of the infinite number of possible ways. Can it explain this?

The fact is established that organisms which vary in such a way as to make them unfitted to carry out the functions which they undertake are destroyed. The correlative fact that organisms which vary in such a way as to perform their functions better than the average are not so usually destroyed, is likewise established. The further fact is established that such congenital variations occur and are often handed on to the offspring. These three facts show that natural selection is beyond question a factor in the development of behavior. The only question is as to the extent of its agency. This depends on the number and extent of the congenital variations that occur. If these are sufficiently numerous and sufficiently varied, then it seems clear that natural selection guided by individual accommodation, would produce the results which we see. Its method of action is exactly what is needed to produce the observed results; the only question is whether the material presented to it in congenital variations is sufficient. The answer to this question must come, if it ever comes, from that study of variations which has received such an impulse in recent years. The recent studies of De Vries in mutation seem especially promising from this point of view. If it should appear that the material presented by congenital variations is not sufficient to account for the observed development, we should be forced apparently to turn once more to the possibility of the inheritance of the characteristics developed during the lifetime of the organism. The question of the inheritance of acquired characters cannot as yet be considered finally settled.

The view that the development of behavior is based largely on selection from among varied movements, with subsequent retention of the selected movements, to which we have come through a study of the behavior of the lower organisms, is of course not a new one. A theory to this effect has been set forth by Spencer and Bain, and has been especially developed in recent years by J. Mark Baldwin. The observations set forth in the present work lead to views differing in some important respects from these developed by Baldwin and Bain, particularly as to the nature of the causes which produce the varied movements. Space will not permit our entering here into a discussion of these differences. The reader may be referred for a discussion of some of the general bearings of this theory to the two volumes of Baldwin (1897, 1902). Possibly the most lucid statement of this theory, in its general bearings, is that recently given by Hobhouse (1901).

In describing the behavior of lower organisms we have used in the present work, so far as possible, objective terms — those having no implication of psychic or subjective qualities. We have looked at organisms as masses of matter, and have attempted to determine the laws of their movements. In ourselves we find movements and reactions resembling in some respects those of the lower organisms. We draw away from heat and cold and injurious chemicals, just as Paramecium does. Our behavior depends on physiological states, as does that of Stentor. But in ourselves there is the very interesting additional fact that these movements, reactions, and physiological states are often accompanied by subjective states, — states of consciousness. Different states of consciousness are as varied as the different possibilities of reaction ; indeed, more varied. In speaking of behavior in ourselves, and as a rule in higher animals, we use terms based on these subjective states, as pleasure and pain, sensation, memory, fear, anger, reason, and the like.

The peculiarity of subjective states is that they can be perceived only by the one person directly experiencing them, — by the subject. Each of us knows directly states of consciousness only in himself. We cannot by observation and experiment detect such states in organisms outside of ourselves. But observation and experiment are the only direct means of studying behavior in the lower organisms. We can reason concerning their behavior, and through reasoning by analogy we may perhaps conclude that they also have conscious states. But reasoning by analogy, when it is afterward tested by observation and experiment, has often shown itself fallacious, so that where it cannot be tested, we must distrust its conclusiveness. Moreover, in different men it leads to different conclusions, so that it does not result in admitted certainty. Hence it seems important to keep the results of observation and experiment distinct from those of reasoning by analogy, so that we may know what is really established. On this account it is customary among most physiologists not to use, in discussing the behavior of the lower organisms, psychic terms, or those implying sub-

jective states. This has the additional ground that the ideal of most scientific men is to explain behavior in terms of matter and energy, so that the introduction of psychic implications is considered superfluous. While this exclusive use of objective terms has great advantages, it has one possible disadvantage. It seems to make an absolute gulf between the behavior of the lower organisms on the one hand, and that of man and higher animals on the other. From a discussion of the behavior of the lower organisms in objective terms, compared with a discussion of the behavior of man in subjective terms, we get the impression of complete discontinuity between the two.

Does such a gulf actually exist, or does it lie only in our manner of speech? We can best get evidence on this question by comparing the objective features of behavior in lower and in higher organisms. In any animal outside of man, and even in man outside of the self, the existence of perception, choice, desire, memory, emotion, intelligence, reasoning, etc., is judged from certain objective facts — certain things which the organisms do. Do we find in the lower organisms objective phenomena of a similar character, so that the same psychic names would be applied to them if found in higher organisms? Do the objective factors in the behavior of lower organisms follow laws that are similar to the laws of psychic states ? Only by comparing the objective factors can we determine whether there is continuity or a gulf between the behavior of lower and higher organisms (including man), for it is only these factors that we know.

Let us then examine some of the concepts employed in discussions of the behavior of higher animals and man, determining whether there exist any corresponding phenomena in lower organisms. We shall not attempt to take into consideration the scholastic definitions of the terms used, but shall judge of them merely from the objective phenomena on which they are based. When we say that an animal perceives something, or that it shows perception of something, we base this statement on the observation that it reacts in some way to this thing. On the same basis we could make the statement that Amoeba perceives all classes of stimuli which we ourselves perceive, save sound (which is, however, essentially one form of mechanical stimulation). Perception as judged from our subjective experiences means much more: how much of this may be present in animals outside the self we cannot know.

Discrimination is a term based, so far as objective evidence goes, upon the observed fact that organisms react differently to different stimuli. In this sense Paramecium, as we have seen, discriminates acids from alkalies ; Amoeba discriminates a Euglena cyst from a grain of sand, and in general all lower organisms show discrimination in many phases of their behavior. Choice is a term based objectively on the fact that the organism accepts or reacts positively to some things, while it rejects or reacts negatively or not at all to others. In this sense all lower organisms show choice, and at this we need not be surprised, for inorganic substances show a similar selectiveness. The distinctive thing about the choice of organisms is that it is regulatory ; organisms on the whole choose those things which aid their normal life processes and reject those that do not. This is what justifies the use of the term "choice," as contrasted with the mere selectiveness of inorganic reactions. Choice in this regulatory sense is shown by lower organisms, as we have seen in detail in previous chapters. Choice is not perfect, from this point of view, in either lower or higher organisms. Paramecium at times accepts things that are useless or harmful to it, but perhaps on the whole less often than does man.

The methods by which choice is shown in particular organisms have been set forth in our descriptive chapters. We may refer particularly to the account of choice in the infusoria, given on page 183. The freeswimming infusoria as they move about are continually rejecting certain things and accepting others, and this choice is regulatory. Their behavior is based throughout on the method of trial, and this involves an act comparable to choice in almost every detail. Whatever the condition met, the infusorian must either accept it by going ahead, or reject it by backing and giving the avoiding reaction. We can almost say that its whole behavior is a process of choice; that choice is the essential feature of its behavior. For the other lower organisms that we have taken up, a consideration of details would discover activities involving regulatory choice almost as continuously as in the infusoria.

Is not what we call attention in higher organisms, when considered objectively, the same phenomenon that we have called the interference of one stimulus with the reaction to another? At the basis of attention lies objectively the phenomenon that the organism may react to only one stimulus even though other stimuli are present which would, if acting alone, likewise produce a response. The organism is then said to attend to the particular stimulus to which it responds. This fundamental phenomenon is clearly present in unicellular organisms. Stentor and Paramecium when reacting to contact with a solid "pay no attention" to a degree of heat or a chemical or an electric current that would produce an immediate reaction in a free individual. On the other hand, individuals reacting to heat or a chemical may not respond to contact with a mass of bacteria, to which they would under other conditions

react positively. In our chapter on reaction under two or more stimuli in the infusoria, many examples of this character are given. Indeed, attention in this objective sense seems a logical necessity for the behavior of any organism having at its command more than a single action. The characteristic responses to two present stimuli may be incompatible with each other. The organism must then react to one or the other, since it cannot react to both; it thus attends (objectively) to one, and not to the other. Only in case there is no reaction at all in the presence of two stimuli, or in case its reaction is precisely intermediate between those required by the two, could the basis of attention be considered lacking. i\n organism behaving in this way would be quickly destroyed as a result of its indecisive and ineffective behavior.