Paramecium

“ These are usually inclined backward and their stroke then drives the animal forward. The most interesting characteristic of the stroke is its obliqueness so that Paramecium always rotates on its long axis, whether it moves forwards or backwards. In consequence of this fact, according to Jennings, Paramecium solves the problem of how an unsymmetrical organism, without eyes or other sense organs, may, nevertheless, maintain a definite course through trackless water. Not even man succeeds in maintaining a straight course under similar but simpler conditions. ”

“ In some of the best-known forms of Protozoa, notably in Paramecium caudatum, the conditions are quite different from those of the majority of protozoa and too many generalizations have been made upon the comparatively rare phenomena which are manifested in this "slipper animal" and its immediate allies. In the conjugation of Paramecium two individual cells unite very much as do Blepharisma cells. In each individual there are two types of nuclei, one, a large macronucleus, plays no part in the fertilization process, but, sooner or later, disintegrates and dissolves in the cell. ”

“ They are sufficiently large to be observed by the common lens, or eye-glass. Paramecium aurelia appears chiefly in vegetable infusions. It is common in ditches and moats with aquatic plants.
Humboldt's assertion is fully verified in the case of the Infusoria under consideration, which is often found with its parasites. These are small creatures, cylindrical in form, and provided with suckers. Swimming vigorously in the water, they devote themselves to chasing the Paramecium. When they have overtaken the fugitive, they throw themselves upon it, and establish themselves there. ”

“ A short parenthetic section on the behaviour of plants may serve further to illustrate the nature of organic behaviour. We have seen that Paramecium is apparently attracted by faintly acid solutions, and have briefly considered Dr. Jennings’s interpretation of the facts disclosed by careful observation. In the ferns the female element, or ovum, is contained in a minute flask-shaped structure (archegonium) , in the neck and mouth of which mucilaginous matter, with a slightly acid reaction, is developed ”

“ Ehrenberg that no fewer than 268 millions might be produced in a month from a single Paramecium;" [3] and even this astonishing rate of increase is far exceeded in another species, one individual of which, "only to be perceived by means of a high magnifying power, is calculated to generate 170 billions in four days." [4] Amongst the larger organisms exhibiting this lowest mode of reproduction under a modified form—that of gemmation—we see that, though not nearly so rapid as in the Infusoria, the rate of multiplication is still extremely high. ”

“ The whole animal is constituted by a single cell, somewhat less than one-hundredth of an inch in length, the form and behaviour of which may be readily studied under the microscope. Thousands may be obtained from water in which some hay has been allowed to rot. The surface of the Paramecium is covered with waving hair-like cilia, by which it is propelled through the water, while stiffer hairs may be shot out from the surface at any point where there is a local source of irritation, as indicated at the top of the accompanying figure. ”

“ Why the automatic mechanism controlling the direction of movement should produce a helical spiral in paramecium, a wavy path or flattened spiral in ameba, and a series of spirals in man, is not yet subject to profitable discussion, except of course to point out that paramecium is not restricted to two dimensions of space as is ameba and man. ”

“ Apparent "positive taxies" are often really negative ones; for if the Paramecium be placed in water containing CO2 it shows the reaction not on entering the part charged with this acid, but on passing away from it into purer water, so that it continually tends to turn back into the acid part, while within it or in the water at a distance not yet charged it swims about irregularly. It appears due to this that the individuals become aggregated together, as they excrete this gas into the water. ”

“ In this way it alters its axis of progression when it finds itself under conditions of stimulation. Thus a Paramecium coming into a region relatively too cold, too hot, or too poor in CO2 or in nutriment, alters its direction of swimming; in this way individuals come to assemble in crowds where food is abundant, or even where there is a slight excess of CO2. ”

“ Jennings’s observations on Paramecia seem to show that the retention of favourable stimulation is not due to its direct influence, but is the indirect result of a reaction to the relatively unfavourable stimulation which occurs when the Paramecium passes away from more satisfactory surroundings. A favourable environment is secured through the avoidance of the unfavourable. ”

“ When positive it determines a movement on to the surface, or a gliding movement along it, or merely the arrest of motion and prolongation of contact; when negative, a contact is followed by the retreat of the being. Thus Paramecium (Fig. 55, p. 151) and many other Ciliates are led to aggregate about solid particles or masses of organic débris in the water, which indeed serve to supply their food. On contact, the cell ceases to move its cilia except those of the oral groove ”

“ Paramécium aurélia (fig. 28) has the body oblong or oblong-ovate, the mouth being placed near the anterior third of its under part. This infusorium is{162} of comparatively large size, and is often found in immense numbers in infusions, which it renders milky. It is admirably adapted for showing the sacculi, which are easily filled with indigo. The body exhibits two remarkable stellate organs, consisting of a central contractile vesicle, surrounded by several radiately placed oval vesicles, which may be seen to contract and dilate with great regularity. The body is coated with very fine cilia. ”

“ The swarm of specimens before us belong to one species, Paramecium aurelia, the Chrysalis animalcule, and they crowd every portion of the little water-drop we have taken up, and examined with a power of about one hundred linear. When they are sufficiently quiet a power of about four hundred may be used with advantage, and Pritchard recommends adding a little indigo and carmine to the water, in order to see the cilia more clearly, or rather to render their action more plain. ”

“ The amœba belongs in the class of protozoans called Rhizopoda “root footed.”
Other classes of Protozoans are the Infusorians (in the broad sense of the term) , which have many waving cilia (Fig. 17) or one whiplike flagellum (Fig. 18) , and the Foraminifers, which possess a calcareous shell pierced with holes (Fig. 19) . Much chalky limestone has been formed of their shells. To which class does the paramecium belong?
Protozoans furnish a large amount of food to the higher animals. ”

“ The rotational streaming continues until the entire filament is wound up, which in exceptional cases may make four or five coils inside the animal.
The mouth has considerable grasping power. This is shown in Figure 32 where a filament of Oscillatoria was bent upon itself by the mouth and then rolled up in the body by the endoplasm in the same manner as a single filament. The mere viscosity of the endoplasm would be insufficient to bring about the bending of the filament. For the sake of comparison it should be added that a similar grasping power is also present in paramecium. ”

“ In the case of Paramœcium the process of multiplication is slightly more complex than that of Amœba in the fact that sometimes before the simple fission of the body takes place the interesting phenomenon of conjugation occurs. Paramœcium may reproduce itself for many generations by simple fission, but a generation finally appears in which conjugation takes place. Two individuals come together and each exchanges with the other a part of its nucleus. ”

“ Paramœcium may occasionally be found reproducing. This process takes place very much as in Amœba. The animal remains dormant for a while, the micronucleus then divides, the macronucleus elongates and finally divides in two, the protoplasm of the body becomes constricted into two parts, each part massing itself about the withdrawn halves of the macro- and micro-nuclei, and lastly the whole breaks into two smaller organisms which grow to be like the original. ”

“ The protoplasm contains oval masses, which are bright green in color; but the forward pointed end of the cell is colorless, and has a little depression. At this end there is a long vibratile protoplasmic filament (c) , by means of which the cell moves. There is also to be seen near this end a red speck (e) which is probably sensitive to light. A nucleus can usually be seen if the cell is first killed with an iodine solution, which often will render the flagellum (c) more evident, this being invisible while the cell is in motion. The cells multiply by division. ”

“ By careful focusing it is easy to show that the protoplasm is confined to a thin layer lining the wall, the central cavity of the tube being filled with cell sap. In the protoplasm are numerous elongated chloroplasts (cl.) . and a larger or smaller number of small, shining, globular bodies (ol.) . These latter are drops of oil, and, when the filaments are injured, sometimes run together, and form drops of large size. No nucleus can be seen in the living plant, but by treatment with chromic acid and staining, numerous very small nuclei may be demonstrated. ”

“ If a little of the fermenting liquid is examined microscopically, it will be found to contain great numbers of very small, oval cells, with thin cell walls and colorless contents. A careful examination with a strong lens (magnifying from 500–1000 diameters) shows that the protoplasm, in which are granules of varying size, does not fill the cell completely, but that there are one or more large vacuoles or spaces filled with colorless cell sap. No nucleus is visible in the living cell, but it has been shown that a nucleus is present.
If growth is active, many of the cells will be seen dividing. ”

“ This is quite proven now, and the statement as it stands is quite correct; but far better and more minutely worked out cases are to be found amongst the Infusoria. In Paramœcium for example, there are normally present a large macronucleus and a small micronucleus lying alongside of it. When two individuals adhere preparatory to conjugation, the macronucleus breaks up into fragments which are absorbed: the micronucleus—which has some time previously divided into two—begins to break up further and eventually forms eight bodies ”

“ Although protoplasm itself is made only of carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus, 178it can make use of a great many other things. When the protoplasm of certain cells wants to build hard, tough walls, it uses potash and soda or even silica, which you know glass is made of. Just draw a blade of sedge grass through your fingers if you want to feel the silica in it. You will probably cut your fingers, but that will help make you remember about silica. Then the protoplasm uses iron to color the petals and other parts of the plant. ”

“ If tentacles with cells containing only very pale pink fluid, and apparently but little protoplasm, are placed in a few drops of a weak solution of one part of the carbonate to 4375 of water (1 gr. to 10 oz.) , and the highly transparent cells beneath the glands are carefully observed under a high power, these may be seen first to become slightly cloudy from the formation of numberless, only just perceptible granules, [5] which rapidly grow larger either from coalescence or from attracting more protoplasm from the surrounding fluid. ”

“ What makes protoplasm and its modifications still more marvellous is the power it possesses of absorbing and moulding a number of other elements in various parts of living organisms for special uses. Such are silica in the stems of the grass family, lime and magnesia in the bones of animals, iron in blood, and many others. Besides the four elements constituting protoplasm, most animals and plants contain also in some parts of their structure sulphur, phosphorus, chlorine, silicon, sodium, potassium, calcium, magnesium, and iron ”

“ The aggregating process spreads from the glands down the pedicels of the hairs; and we may assume that any matter which is absorbed ultimately reaches the tissues of the plant. On the other hand, the process travels up the hairs whenever a surface is cut and exposed to a solution of the carbonate of ammonia.
The glands on the flower-stalks and leaves of Primula sinensis quickly absorb a solution of the carbonate of ammonia, and the protoplasm which they contain becomes aggregated. The process was seen in some cases to travel from the glands into the upper cells of the pedicels. ”

“ The chromacea, as protophyta, are plasmodomous. They form new plasm by synthesis and reduction from simple inorganic compounds—water, carbonic acid, ammonia, nitric acid, etc. But the bacteria, as protozoa, are plasmophagous. They cannot, as a rule, form new plasm, but have to take it from other organisms (as parasites, saprophytes, etc.) ; they decompose it by analysis and oxydation. Hence the [201] colorless bacteria are without the important green, blue, or red coloring matter (phycocyan) which tints the plastids of the chromacea, and is the real instrument of the carbon-assimilation. ”