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

However, doubts exist upon the question as to whether Proto-organisms know the direction and distance of external bodies, or whether they only succeed in getting at them after a series of tentative movements. The observations which we have collated do not solve the question. 4. Motory phase. — We now pass to the motory phase. The movements made by Micro-organisms as if in response to an excitation, are not in most instances simple reflex motions; they are movements adapted to an end. We cannot repeat it too much: these movements are not explained by the simple phenomenon of cellular irritability.

In the very first instance, they vary according to the excitation; a given excitation produces a corresponding motory response; a body situated at the right does not bring about the same movement that a body situated at the left does; a particle of the nutritive sort does not provoke the same course of action that a particle of a different sort does. All this implies that associations have been established in the protoplasm between certain excitations and certain movements. The explanation of the physical nature of these association appears to us totally impossible.

The quite ingenious ideas broached by Spencer upon the lines of least resistance offered by the commisural fibres cannot be applied here, since everything takes place in a single cell. What would be necessary to explain is how and in consequence of what mechanism of structure one form of molecular movement, corresponding to a given excitation, is followed by a certain other form of molecular movement corresponding to an act likewise determined.

We now enter upon a subject fraught with obscurity. We shall limit our investigations to ciliated In- fusoria, as it is among these species that fecundation and the psychical phenomena attendant thereon have been best observed. Ehrenberg had established by his authority the prevailing opinion in science that copulation never takes place among Infusoria, and that all facts observed by early writers as connected therewith are to be regarded as phenomena of longitudinal fissiparity. This erroneous idea prevailed unquestioned until 1858, when M. Balbiani addressed a communication to the Academy of Sciences, wherein he showed that sexual

reproduction, preceded by copulation, is found among Infusoria. Before entering upon a description of the changes that take place in the nucleus and nucleole of Infusoria in coition, we shall briefly sketch the course of psychical phenomena through which the ciliated Infusoria pass when making ready for copulation. We shall follow in the footsteps of M. Balbiani, freely using his descriptions, the exactitude of which has since been confirmed by Gruber.

To appreciate fully the significance of the facts to be adduced herewith, we must recall to mind that throughout the entire animal kingdom the act of sexual coition is invariably preceded by an introductory manifestation of psychical activity, which may last for quite an extended length of time. The female, when pursued by the male, seems to be animated by two conflicting desires — that of yielding to the male and that of repelling his approaches. This show of unwillingness, which is but temporary and more seeming than real, has the effect of inciting the male to attempt an exhibition of powers calculated to captivate the female. According to M. Espinas, who has thoroughly studied this subject, there are five classes of phenomena which assist in preparing the way for sexual union: firsfl^, provocative contact, the lowest of all these phenomena — that is, the one which most approximates to the physiological order; secondly, odor; thirdly, color and form; fourthly, noise and sound; fifthly, play, or every variety of movement. It appears to us that almost all manifestations of love in human beings themselves could be classified into these five categories.

cipient traces of such aesthetical manifestations pointing towards the preparation of two animals for sexual intercourse. " It is curious," remarks M. Balbiani, " to find among these organisms which all zoologists, by reason of their diminutive size and extreme simplicity of structure, have placed at the remotest limit of the animal kingdom, acts that mark the existence of phenomena analogous to those by which the sexual instinct is 'exhibited in a large number of Metazoans. Upon the approach of the period for propagation, the Paramecia come in from all points of the fluid and assemble like little whitish clouds in more or less numerous groups about the objects that float upon the surface of the water, or adhere to the side of the vessel containing the tiny artificial sea in which the animalculaoare held captive. Intense excitement, which the need of food does not suffice to explain, prevails in each of these groups; a higher instinct appears to dominate all these tiny organisms; they seek each other's company, chase each other about, feel here and there with their cilia, adhere for a moment or so in an attitude of sexual coition, and then retire, soon to begin anew. When these minute assemblages are dispersed by shaking the liquid, they quickly form again at other points. These singular antics wherewith animalculaxappear to incite each other mutually to copulation often continue for several days before the latter act is definitely effected.

" Other Infusoria, particularly the Spirostomes, seek the deep spots of the liquid, or bury themselves in the oozy sediment of the bottom, not to come forth again until they have separated. The Stentors have different habits. They are affixed by their pedicles to submerged vegetable patches, which they often cover like small, closely-mown lawns, of a green, brown, or blue color, according to the species; they turn the forward part of their bodies, which is elongated in the shape of a trumpet, about in all* directions, and seek to unite with each other by the broadened extremity which corresponds to the bell of the trumpet."

Among the numerous species forming part of the group of Oxytrichinae, the act of coition likewise exhibits certain interesting preliminaries. The two individuals, whose bodies are generally very much flattened, and of which the lower sides are provided with cilia at times strongly developed, superpose\hemselves upon each other on the ventral side and mutually entangle the cilia which cover that region, while with their cornicles, or anterior tentacles, they touch repeatedly the different parts of each other's bodies. These introductory moves frequently last for several hours before copulation begins.

As regards the act of copulation itself, it too is of exceeding interest to the psychologist, who can admire the precision with which the two individuals assume the attitude necessary for fecundation. During conjugation the two ciliated Infusoria are always joined together at the aperture which forms the mouth. It has been thought that this aperture must play the part of a sexual orifice through which the two animalculac in copulation effected the exchange of reproductive matter; it has been suggested, moreover, that an especial sexual orifice was present, quite close to the mouth; but these questions of structure are still doubtful.

varies according to the position of the mouth which in certain groups is lateral and in others terminal, The greater number of species have a lateral mouth. To this class belong the Paramecia; these Infusoria, in which the buccal fosse lies at the bottom of a deep excavation made in the ventral face, cover each other over the whole extent of this face, exuding a glutinous substance which causes them to adhere in this position; the two mouths then lie exactly upon each other. Copulation lasts from twenty-four to thirty-six hours with the Paramczcium au'relia; it lasts several days (five or six) with the Paramcecium bursaria. Among the Oxytrichinae, the two animals in conjugation blend together at an important part of their persons in a very intimate fashion.

We next arrive to the second group of Infusoria, which show a terminal mouth; of this type we have had a specimen in the Didinium nasutum, the curious hunter Infusory; we may .further mention the Coleps, the Nassula, the Prorodon. The two organisms, in this case, do not embrace laterally, they take a position end to end, connected by fheir anterior extremities, mouth opposite to mouth; then, little by little, while still joined at the buccal extremity, they shift about until they meet length to length.

We shall mention particularly, but briefly, the curious phenomena that accompany fecundation among the Vorticels. Even more than in the instances just cited do these phenomena resemble the process of fecundation in higher animals, for in this instance fecundation is effected between two differentiated individuals, one of which acts as a male element and the other as a female element. The Vorticels are colonies of In- fusoria in which are found sedentary individuals,

having the shape of minute jugs, and also detached individuals called Microgonidia, which are formed by repeated divisions upon the colonial tree. These Microgonidia have exactly the same mode of locomotion as the spermatozoids. Engelmann * has followed their movements. He has seen them swimming about turning upon their axis for five or six minutes; then, having come into the vicinity of a Vorticel, they abruptly change their manner of movement, capering about the latter like a butterfly flitting about a flower, touching it, retreating, and then approaching it again and apparently feeling of it; at last, after having visited the others near by, they return to the first one and fasten themselves upon, its surface. The coition is not effected without a certain show of resistance on the part of the Vorticel. It hastily contracts the peduncle to which it is attached, at every touch of the Microgonidium, while the latter in order to prevent itself from being thrown back by these rapid shocks and in order to be always close to the individual with which it wishes to unite, fastens itself by an extremely fine -filament to the style of the Vorticel; thus attached and drawn along with the movements of the latter, it finally succeeds in effecting a junction with it and in penetrating into its body.f

It is now time to describe the material phenomena that take place in the interior of the two Infusoria, and which constitute the material act of fecundation. The psychical manifestations which we have just noted and which so strikingly resemble the manifestations accompanying the copulative act in higher animals, are of themselves sufficient evidence that this conjugation is a sexual union. The material changes effected inside the bodies of Infusoria in copulation do not extend to all their organs; the main mass of the body, the protoplasm, plays but a secondary role in the matter; the change appears to be effected exclusively in the nucleus and the nucleole.

Let us further state that, so far as is known, these changes are never effected apart from coition and before the Infusoria actually embrace; copulation sets in every time, apparentJy, that these animals, under particularly favorable conditions, have actively reproduced by fission. Fissiparity is then seen to cease and conjugation appears. We have not the time to sketch the history of this important question of physiology, interesting as it may be. It will be enough to recapitulate what we actually know upon the subject, taking as our guide substantially the views of M. Balbiani who, as is known, was the first scientist to study the physical phenomena connected with fecundation among Infusoria. The divergencies between his observations and those of another eminent investigator, M. Biitschli, extend in reality only to points of detail.

Let us first mark the modifications that take place within the Chilodon cucullus during conjugation. Each of the two Infusoria in copulation possesses a nucleus (endoplast, main nucleus) and, close beside this nucleus, an organ considerably smaller, a nucleole, or attendant nucleus, or latent nucleus (endoplastule, accessory nucleus); this minute body must not be mistaken for the nucleole that is often found in the interior of the nucleus among many Micro-organisms and in cellules; it has a function entirely different.

most negative part in the act of fecundation. It assumes irregular outlines and becomes rumpled, while its contents collect in detached masses of various sizes: it grows clear by degrees and is finally absorbed. It disappears, accordingly, by a phenomenon of regression and without dividing. Fecundation aims to replace this wasted element by a nucleus of fresh formation. The latter is produced at the cost of the little body we have described by the name of attendant nucleus or latent nucleus. The attendant nucleus does not act in making up a main nucleus in the cellule of which it is a part; it finds its way into the body of the other animal and it is in this new cellule that it is destined to perform the function of a nucleus.

In the Chilodon cucullulus, the attendant nucleus divides into two striated capsules, never more. These two capsules grow to unequal sizes; the largest attains a size of forty thousandths of a millimetre; it is this one that forms the new nucleus of the Chilodon. The second capsule shrinks and becomes compressed; it takes its place beside the first one and constitutes the new attendant nucleus. To the study of this type of fecundation we may limit our attention; it is the simplest of all, and other forms may be comprehended within it without much difficulty. What complicates the process* in the other species is principally the successive modifications through which the old nucleus passes before suffering absorption. In the Stentor cceruletisthe, nucleus has the shape of a long chaplet or string of beads; at the moment of fecundation the beads of the chaplet break apart and spread in the protoplasm where they finally become absorbed. Among the Paramaecia the phe-

nomenon is still different: the nucleus, at first massed together in a cluster, lengthens out into a very long string, which breaks; and the pieces becoming scattered about in the protoplasm, are absorbed. We find that fecundation in every instance introduces the dispersion and disappearance of the old nucleus and that the latter is replaced by a new nucleus resulting from the transformation of the attendant nucleus that proceeded from the other organism.

The various modifications presented by this attendant nucleus likewise contribute in great measure to the complexity of the phenomenon. We have seen that in the Chilodon the attendant nucleus breaks into two globules, of which one goes to form the new nucleus and the other the new attendant nucleus. Matters take a different course in the Paramaecia. In the Paranuzcium frursaria, for instance, the attendant nucleus divides into two and then into four capsules; one of these capsules suffers absorption, a second one becomes the attendant nucleus, and the two others coalesce with what remains of the old nucleus to form the nucleus proper. In the Paramacium aurelia the division is made into eight capsules; three are cast out, and of the five left four are meant to form the new main nucleus; in reality, each Paramaecium segmentates first into two and then into four divisions, and each of these four individuals takes one of the capsules. The fifth capsule is designed to -form the attendant nucleuses of these four organisms; it divides, accordingly, into two and then into four parts; that is to say, into as many parts as the body of the animal divided.

There is no question in our mind but that conjugation in this case is a sexual phenomenon. A circumstance that at the outset confirms this is the peculiar manceuvering the animalcula go through before abandoning themselves to copulation; the movements they execute admit of exact comparison with the actions attendant upon copulation among higher animals. But we shall recur further on to the physiological significance of conjugation, when we shall endeavor to explain, according to the most recent investigations, the function of the nucleus in the cellule.

The question may be asked, what is the startingpoint, the provocative of these sexual phenomena, the cause that sets them in play. Biitschli justly thinks, that conjugation is determined by internal causes; in fact, it takes place directly after very active periods of spontaneous division, as Balbiani has shown. When we bear in mind that the object of conjugation is to replace the old nucleus which has become wasted and worn out, we may conjecture with some degree of likelihood that the physiological condition of the nucleus constitutes the sexual excitant that causes the Infusoria to copulate.

However that may be, a curious observation witn the ParamcEcium aurelia has made us acquainted with one of the structural conditions of the sexual instinct in that Infusory. For a long time J. Miiller had pointed to the presence of filaments in the nucleus and even nucleolus of Paramaecia, that had the appearance of spermatozoids. Observations to the same effect have increased since then, and it is now known that the filaments are Schizomycetes, parasitic Bacilli, which find their way into the nucleus and nucleolus, and multiply, after their customary mode of segmentation, by disarticulation. Balbiani has definitely determined the nature of these filaments by morphological and micro-chemical methods; he has found out, among

other things, that the filaments do not dissolve in strongly concentrated alkaline solutions; and it is known that Bacteria exhibit this peculiar attribute of offering a great resistance to destructive agents. In the nucleus which they have penetrated, these parasites induce a pathological condition that results in destroying every manifestation of the sexual instinct in this Infusory. Among a swarm of animals of this species that are in copulation, single individuals are found that show a nucleus and nucleolus corncompletely charged with Bacteria; sometimes these organs surfer an enormous dilatation, the nucleus becoming nothing more than an enveloping membrane which is filled like a huge pouch with parasites. The animal continues to live, but it no longer attempts to copulate.

It is not our intention to make a full and complete study of fecundation in higher animals and plants; there is but one phase of that phenomenon that can enter into a general study of Micro-organisms, and that is the history-of the sexual elements, of their form, their movements, and lastly their copulation. We shall describe animal fecundation first, and plant fecundation afterwards; regarding these phenomena particularly from a psychological standpoint.

Among metazoans, fecundation may be divided into two distinct acts. The first, and most apparent, consists of the union of the two individuals; of this we shall not have to speak here; it is a phenomenon that lies outside the limits of our investigations. The second, more deep-seated, consists in the phenomena that take place, after copulation, between the spermatozoid and the ovule. There are numerous reasons for comprehending a study of the generative elements within a general investigation into the nature of Micro-organisms.

In the very first place, it must be taken into account, that these two elements are represented in animals by a single cell. The ovule appears as a minute microscopic sphere enclosed by an envelope (vitelline membrane); it is formed of a mass of granulous protoplasm (vitellus) containing a nucleus (germinative vesicle) and one or many nucleoli (germinative spot). The spermatozoids, in vertebrates, have quite a different aspect: they are filaments of varying lengths, having a distended part, or head, and a tapering, attenuated part, or tail.

The resemblance that spermatozoids bear to Protista, at first caused them to be regarded as animals living a parasitic life in the spermatic fluid. Ehrenberg classed them among the polygastric Infusoria. Kcelliker and Lallemand were the first to reject this notion and the first toregard spermatozoids as elemental parts of living tissues, having the morphological value of a cellule. They are now likened to detached cellular elements, such as blood-globules.

Whatever form they assume, the sexual elements live as minute organisms independent of the individual from which they originated. This circumstance is particularly remarkable in the case of the male element, the spermatozoid, which retains its vitality for a certain space of time after its expulsion. The length of this period varies with the different species. Whereas the spermatozoids thrown from a trout lose all motion in the water after the expiration of a few seconds,