The Psychic Life of Micro-organisms: A Study in Experimental Psychology

T HAVE endeavored, in the following essay upon Micro-organisms, to show that psychological phenomena begin among the very lowest classes of beings; they are met with in every form of life from the simplest cellule to the most complicated organism. It is they that are the essential phenomena of life, inherent in all pro toplasm. We admit, accordingly, the existence of a vitalism, that is to say, of an aggregate of properties which properly pertain to living matter and which are never found in inanimate substances. Among these properties «of life we classify psychological phenomena.

Vitalism, it is unnecessary to say, has nothing in common with the doctrine upheld by the School of Montpellier. The principle here involved has nothing to do with properties and forces that are superadded to living matter; it concerns the properties that are inherent in it — the properties that characterize life. The modern opponents of vitalism seek to confute the theory by attempting to explain all phenomena of life from physico-chemical forces. They maintain that according as physiology advances the tendency is to relegate all phenomena nominally physiological into the domain of physics and chemistry; and that it would be only a question of time, if as yet they had not succeeded in demonstrating that every vital process is founded upon mechanical phenomena.

In a recent treatise upon "Vitalism and Mechanism,"* M. Bunge, professor of physiology at Basel, has shown that the history of physiology disproves these hypotheses. The more closely the phenomena of life are scrutinized, the more carefully they are studied in their various aspects, the more certain does the conclusion become that the processes attributed to physico-chemical forces in reality obey much more complicated laws. To illustrate, it was at one time conceded that the phenomena of resorption and nutrition were explainable by diffusion and endosmosis; Dutrochet, upon his discovery of endosmosis, imagined even that he had discovered the principle of life. At the present time we know that the •walls of the intestines do not in any wise act like the inanimate membrane used in experiments in endosmosis. They are covered with epithelial cells, each of which is an organism endowed with a complex of properties. The protoplasm of these cells lays hold of food by an act of prehension, exactly as the ciliate Infusoria and other unicellular organisms do, that lead an independent life. In the intestines of cold-blooded animals the cells emit prolongations wnich seize the minute drops of fatty matter and, carrying them into the protoplasm of the cell, convey them therice into the chylifactive ducts. There is still another mode of absorption of fatty matters, met with among cold-blooded as well as warm-blooded animals: the lymphatic cells pass out from the adenoid tissue which contains them, so that upon arriving at the surface of the intestines they seize the particles of fatty matter there present and, laden •with their prey, make their way back to the lymphatics.

Accordingly, the faculty of seizing food and of exercising a choice among foods of different kinds — a property essentially psychological—appertains to the anatomical elements of the tissues, just as it does to all unicellular beings, in the manner shown in our treatise. It is plainly impossible to explain these facts by the introduction of physico-chemical forces. They are the essential phenomena of life and are the exclusive appurtenance of living protoplasm.

If the existence of psychological phenomena in lower organisms is denied, it will be necessary to assume that these phenomena can be superadded in the course of evolution, in proportion as an organism grows more perfect and complex. Nothing could be more inconsistent with the teachings of general physiology, which shows us that all vital phenomena are previously present in nondifferentiated cells. Furthermore, it is interesting to note to what conclusion the admission would lead — as Romanes apparently does admit — that psychological properties are wanting in lower-class beings and that they enter at different stages of zoological development. Romanes has minutely particularized on a large chart the development of the intellectual powers, in quite an arbitrary manner. According to his scheme, only protoplasmic movements, and the property of excitability are present in lower-class organisms. Memory begins first with the echinoderms; the primary instincts with the larvae of insects and the Annelids; the secondary instincts, with insects and spiders; reason, finally, commences with the higher Crustaceans.

I do not hesitate to say that all this laborious classification is artificial in the extreme, and perfectly anomalous. All writers that have devoted themselves, with any pretension to special investigation, to the study of unicellular organisms, have attributed to these beings most of the psychological properties which M. Romanes reserves for this or that higher-class animal. This is the opinion of Gruber, of Verworn, of Moebius, of Balbiani, and of many other naturalists. Moebius recognizes that psychological life begins with living protoplasm, and he considers it to be the highest aim of zoology to demonstrate the psychical unity of all animals.

We could, if it were necessary, take every single one of the psychical faculties which M. Romanes reserves for animals more or less advanced on the zoological scale, and show that the greater part of these faculties belonged equally to Micro-organisms. But we must not unnecessarily extend the discussions of this introduction. We shall accordingly limit ourselves to few illustrations. M. Romanes, in his zoological scale, assigns the first manifestations of surprise and fear to the Iarva5 of insects and to the An-

nelids. We may reply upon this point, that there is not a single ciliate Infusory that cannot be frightened, and that does not manifest its fear by a rapid flight through the liquid of the preparation. If a drop of acetic acid be introduced beneath the glass-slide, in a preparation containing quantities of Infusoria, the latter will at once be seen to flee from all directions like a flock of frightened sheep. Memory, according to M. Romanes, first begins with the Echinoderms. Now, Moebius, upon the occasion of a treatise upon the Folliculina ampulla* a ciliated Infusory presenting complicated and interesting movements, properly remarks that every time an animal repeats the same action under influence of the same excitations, that fact proves that the animal is possessed of memory. In fact, memory is one of the most elementary of psychological facts.

Lastly, the primary instincts, according to M. Romanes, begin first with the larvae of insects and with Annelids. We give, in contradiction of this statement, the recent observations of Verworn.f which reveal the existence of curious instincts among the Rhizopods. The Di/lugia urceolata, which inhabits a shell formed of particles of sand, emits long pseudopodia which search at the bottom of the water for the materials necessary to construct a new case for the filial organism to which it gives birth by division. The pseudopod, after having touched a particle of sand, contracts, and the grain of sand, adhering to the pseudopod, is seen to pass into the body of the animal.. Verworn, instead of grains of sand, placed small fragments of colored glass about the animal; some time afterwards, he noticed a heap of these fragments on the bottom of the shell. He then saw a bunch of protoplasm issue from the shell, representing the new Diffltigia produced by division. Thereupon, the materials collected by the mother-organism — the fragments of colored glass— came forth from the shell and enveloped the body of the new individual in a sheath similar to that en-

* Mcebius, Das Flaschenthierchen, Folliculina ampulla, 1887. casing the mother. These fragments of glass, loosely interjoined at first, were now cemented together by a substance secreted by the body of the animal. Two facts are to be remarked in this observation: first, the act whereby the Dijflugia collects the materials for providing the young individual with a case, is an act of preadaptation to an end not present, but remote; this act, therefore, has all the marks of an instinct. Further, the instinct of the Dijflugia exhibits great precision; for the Dijflugia not only knows how to distinguish, at the bottom of the water, the materials available for its purpose, but it takes only the quantity of material necessary to enable the young individual to acquire a well-built case; there is never an excess.

It is interesting to note that the Dijflugia does not act differently from animals possessing more highly complicated organizations and endowed with differentiated nervous systems, as for instance, the larvae of Phryganids which form their sheaths from shells, grains of sand, or minute slivers. We shall not regard it as strange, perhaps, to find so complete a psychology in the history of lower organisms, when we call to mind that, agreeably to the ideas of evolution now accepted, a higher animal is nothing more than a colony of protozoans. Hvery one of the cells composing such an animal, has retained its primitive properties, giving them a higher degree of perfection by division of labor and by selection. The epithelial cells that secrete the nails and the hair are organisms perfected with reference to the secretion of protective parts. Similarly, the cells of the brain are organisms that have been perfected with reference to psychical attributes.

A branch of Comparative Psychology little known.— Definition of Micro-organisms. — Their classification. — Main groups of animal Micro-organisms.— Complexity of their life of relation.— The Micro-organism not simply an irritatable cellule... 1-4 Motility. — The pseudopod. — Opinion of M. Rouget relative to the formation of pseudopods. — The vibrat'ile cilia. — Their morphological significance. — Observations of Engelmann. — The movements of the vibratile cilia are subject to the will of the animal. — Observations of M. Balbiani upon the Didinium nasutum. — Experiments of Rossbach. — The flagellum. — Diversity of its movements. — Observation of Biitschli upon the flagellum of the Glenodinium fine turn. — Metabolic infusoria. — The granulous bands and bright filaments. — The contractile vesicle. — The movements of Bacteria and Gregarinae 4-20

Absence of a central nervous system in single-celled organisms.— Hypothesis of a diffused nervous system. — Observation of Gruber upon the Stentor in process of division . 20-22 Organs of touch.— Organs of sight.— Ocular spot in Flagellates.— Ocular spot of vegetable zoospores. — Experiments of Klebs upon the structure of these spots. — The pigment. — Opinion of naturalists upon the physiological function of the so-called ocular spots. — Observation of M. Pouchet upon the eye of the Glenodinium po lyphemus. — This eye is composed of a pigmentary mass and of a refringent body. — Observations of M. Kiinstler upon the eye of Phacus. — Observation of Claparede and Lachmann. — Observation of Lieberkiihn. — Sensitiveness of the Euglena to light. — Experiments of Engelmann. — The vesicles of Miiller in the Loxodes rostrum 22-31

Psychical phenomena connected with respiration. — Search for oxygen by the bacteria of putrefied matter. — Observation of Engelmann 3J-34 Psychical phenomena connected with nutrition. — Vegetable, or holophytic, nutrition. — The chromatophores.— Structure ot the chromatophores. — Coincidence between the presence of an eye and that of chlorophyl pigment. — Comparison between the Euglena and the Peranema. — Nutrition by endosmosis, or saprophytic. — Animal nutrition, choice of nutriment.— Prehension of foods by the Amoeba, the Actinophrys, the Monas, the Acineta. — Opinion of M. Maupas upon choice by preference. — Capture of food. — The vorticelCiliates.— The Hunter Ciliates. — The Amphileptus. — The Didinium nasutum. — Movements of defense and flight 34-55

Colonies of unicellular organisms. — Colonies of single-celled organisms have their origin in the segmentations of a mother-cellule.— Temporary colonies which are formed beneath the cuticle.— The Gonium. — The Eudoryna.— The Volvox. — Difference between a pluricellular organism and a colony of unicellular organisms. — Voluntary combinations.— The Bodo caudatus 55~6i Remarks upon the psychology of Micro-organisms. — Their various actions are direct responses to stimuli from the outward world. — Perception of external bodies. — Choice. — Calculation of the positions occupied by external bodies. — Movements of Micro-organisms 61-65

Fecundation among Infusoria. — Historical. — Psychological preliminaries of fecundation — Observations of M. Balbiani upon the Paramaecia, the Spirostomes, and the Stentors. — Copulation. — Fecundation among the Vorticels. — Observation of Engelmann. — Material phenomena in fecundation.— The role of the nucleus, and the role of the nucleolus. — Description of the phenomena as seen in the Chilodon cucullulus (see appendix), the Paranuzciiim bursaria and in the Param&ciutn aurelia. — Observation of M. Balbiani upon Paramaecia, of which the nucleus is overrun with parasites 65-75

Fecundation in higher animals and plants. — The spermatozoid and the ovule can be compared to Micro-organisms. — The elements can live for a certain time independent of the animals from which they come. — Their motor organs. —The 'movements of the spermatozoid towards the ovule. —Length of road to be traveled.— Obstacles to be overcome.—Windings and intricacies of the path. —The spermatozoid of the silkworm.— Arrival of the spermatozoid in contact with the ovule.— Observation of Fol upon the fecundation of the star-fish.— The cone of attraction.—

Pages Sexual selection operating as between different spermatozoids. — Movements of the female element. — Vegetable fecundation. — Progressive differentiation of the two sexual elements. — Sexual reproduction of the Ectocarpus siliculosus, after Berthold. — Investigations of Pfeffer upon the spermatozoids of cryptogams. — Action of certain chemical excitants upon these elements. — Specific character of the excitant. — The threshold of excitation. — Applition of Weber's law 75~9i

Functions attributed to the protoplasm and to the enveloping membrane. — The nucleus, its histological importance proved by the phenomena of caryokinesis. — Balbiani and Gruber have, at times, observed Infusoria and Actinophrys deprived of nuclear substance. — Nussbaum's and Gruber's experiments of vivisection upon the Stentor cceruleus. — Fragments provided with nucleus reconstruct themselves. — Experiments of Balbiani — Facts observed by Gruber, in general, confirmed. — Error of Gruber respecting fragments without nucleus. — These fragments do not continue to live, their plasma undergoes disorganization. — Experiments of division. — Experiments made upon Infusoria while in conjugation. — The presence of the old nucleus in a severed fragment only brings about an incomplete regeneration. — Th# nucleus presides over all physiological functions, the totality of which constitutes life. — The regenerative and reproductive property of the plasma is lost before the psychical functions are. — Agreement of all these facts with the phenomena observed as taking place during the spontaneous division of Micro-organisms 92-105

Statement of M. Richet's position respecting cellular psychology 105 Pages Romanes's conception of the psychic activity of Proto- Correspondence between Ch. Richet and Alfred Binet, appearing in the Revue Philosophique of February, 1888, reprinted from THE OPEN COURT of December 27, 1888.110-115 The Conjugation of the Chilodon cucullulus (with explanations) 1 18 THE study of microscopic organisms has hitherto been somewhat neglected .by students of comparative psychology. Naturalistswho have devoted their attention to the study of these beings, have collected a great number of interesting facts concerning their psychic life; but these facts have not yet been critically examined and collated; they are scattered in reports and publications of all kinds, where the psychologist never dreams of looking for them. We shall endeavor to make him acquainted with a part of this wealth.

Under the name Micro-organism are included all those beings which by reason of their extreme smallness and simplicity of structure represent the lowest stages of animal or vegetable life; they constitute the very simplest forms of living matter, and consist of a single cell. Some inhabit fresh and salt waters, serving as food for a great many other organisms, or contributing by means of their calcareous or silicious skeletons to the formation of continents. Others live as parasites in the organs of animals and plants, and induce more or less serious disorders in the constitutions Df the organisms they have penetrated. Others, again, acting like ferments produce important chemical modifications in organic matter in the course of decomposition.

A great number of classifications for the methodical distribution of these beings has been proposed; but not one of them is altogether satisfactory; and that stands to reason. If a natural classification is always a complex piece of work in the case of the higher animals which differ from each other in important features and between which a comparison can be instituted, the difficulty attending the classification of simple organisms which present only the slightest differentiations is still more difficult.

The principal division made is that which divides them into animal Micro-organisms or Protozoans and vegetable Micro-organisms or Microphytes. The line of demarcation between these two kingdoms is far from being well defined; there are a great number of micro-organisms incerttz sedis, which botanists usually place in the vegetable kingdom, but which zoologists prefer to classify as belonging to the animal kingdom.* We give below a list of the most important groups of animal micro-organisms.

We propose, now, to study the psychic life of these lower organisms, or, to speak in more general terms, their life of relation. It is well known that the expression, the life of relation, comprehends essentially two distinct ideas: first, the action of the external world felt by the organism: or sensibility; secondly, the reaction of the organism on the external world: or move- *The best mark to distinguish the two kingdoms is the chemical nature of the enveloping membrane: in the case of vegetable organisms, the enveloping membrane is made up of a ternary substance, cellulose: while in animal organisms it is albuminoid in character.

ment. It is customary to apply to the union of these two properties the name irritability, which expresses the reaction of the micro-organism upon exterior forces. It is therefore held, and with reason, that every living cell is irritable, that is to say that it possesses the property of responding by movements to the excitations which it surfers. In admitting then that irritability is the foundation of the life of relation, and consequently also the foundation of psychology, we must nevertheless guard against comparing the autonomous cell of microorganisms to a simple irritable cell. Although the body of these small beings may be equivalent to a simple cell, it would be an error to believe that their life of relation consists in a motory reaction consequent upon exterior irritation. At the close of our investigations into the psychology of Proto-organisms we shall see that, in these inferior beings which represent the simplest forms of life, we find manifestations of an intelligence which greatly transcends the phenomena of cellular irritability. Thus, even on the very lowest rounds of the ladder of life, psychic manifestations are very much more complex than is usually believed, and the conception of cellular psychology which some very recent authors have formed, seems to me a very crude analysis of the most delicate of phenomena.

In the great majority of pluricellular animals, the life of relation is exhibited in a nervous system and in a muscular system. In Micro-organisms the same cannot be said to be the case: the greater part possess neither a central nervous system nor organs of sense; some even lack organs of locomotion. The functions of the life of relation are performed by the entire mass of the body: many of the Protista, for example, have not a trace of an anatomically differentiated visual organ; it is the entire protoplasm of the elementary organism that is excitable by light, as it is also by heat or by electricity. In other Micro-organisms somewhat higher in the scale, a beginning of differentiation may be seen to make its appearance, giving birth either to some organ of sense or to some organ of locomotion.

We shall give a general description of these organs. The study of this first move in the work of differentiation is of great interest to comparative anatomy and physiology; no less interesting is it to psychology. Besides dwelling on these preliminaries of our work, we shall have occasion to note new and interesting facts. Motility. From the schedule of the groups of animal micro-organisms which we have given, it will be seen that they are subdivided into four classes, the Infusoria, the Mastigophores, the Sarcodines and the Sporozoa. The distinction between these classes depends on the existence and the nature of the motor organs.

The Infusoria comprise the protozoa that move by the aid of vibratile cilia distributed in greater or less number over their body. The second class, the Mastigophores, comprises those animals which move by the aid of flagella, that is to say by the help of long filaments. The third class, the Sarcodines, comprises those animals which move by the aid of pseudopodia; which are projections of the substance of their bodies. the mode of multiplication: they are reproduced by spores. In the animals of this group, the special motor organs are wanting; these creatures therefore generally move very little, or they present only movements of which the principles are unknown.

We shall successively describe the pseudopodia, the vibratile cilia and the flagellum. The Pseudopod. The formation of pseudopodia takes place chiefly in naked cells — in cells lacking an enveloping membrane, in the Sarcodines in general. They can easily be studied in the Amoeba princeps, a microscopic animal which is found in abundance in fresh water containing organic matter in a state of putrefaction. It has the aspect of a small gelatinous mass, irregular, formed of a colorless substance, the protoplasm. The chemical nature of protoplasm is still very imperfectly understood; it is only known that it is the result of a mixture of albuminoid matters, with an addition of water and mineral elements. In the protoplasm of the amoeba exists a small rounded and refracting mass, containing one or two bright corpuscles in its interior; this small mass is called the nucleus, and the corpuscles the nucleoli.

The form of the body of the amoeba is rendered very irregular by the fact that certain parts of the mass lengthen, and form short and rounded protuberances which are designated by the name of pseudopodia. It is by means of these pseudopodia that the animal moves; it emits them in the direction in which it is going, then it retracts them, while other parts of the mass are in their turn elongated. The whole body moves by creeping. The amoeba in moving has the aspect of a drop of oil moving along. To explain the mechanism of this movement, it must be supposed