WONDERS OF THE MICROSCOPE

New Zealand Herald, Volume L, Issue 15252, 15 March 1913, Page 1 (Supplement)

WONDERS OF THE MICROSCOPE

NEAR THE BEGINNING OF

ANIMAL LIFE.

EXAMINING THE AMOEBA,

No. 11.

BY G. A. RAWSOK.

Is this bottle before me I have some water taken from a stagnant pond. As you see, it is dirty and discoloured, owing to the quantity of decaying vegetable material which it contains. I now take up a few drops of this water into a pipette and transfer thorn to a hollow depression on a glass slide, which I adjust, on the stage of the microscope, and focus upom them a power of about 300 diameters. Place your eye to the microscope, and look through it. "Good heavens," you exclaim, "it is absolutely alive!" Quito so; you see enormous numbers of creatures, Some crawling and gliding about in a leisurely fashion, as though they were carefully searching for something, and others darting about or spinning and wriggling round each other with such rapidity that it ia almost impossible to identify them, unless you are thoroughly, familiar with them. These are all Protozoa of various kinds, and there are countless millions oil them in the* bottle of water from which I took these few drops. It is quite possible that a higher power still will reveal the presence among them of some of those tiniest and simplest organisms known as Monera, which will be almost indistinguishable from the spores or germs of various species of bacteria, which latter are generally regarded as vegetable organisms. But look! here is an Amoeba at last, creeping about by thrusting out its protoplasmic processes in all directions. Let us transfer it with the pipette on to a it at leisure. What an extraordinary creature it is It will prove a most exciting pastime to watch its incessant transmutations. It is nearly as transparent as the glass, so that we can see entirely through it. Nothing worthy of being called organisation can be discovered in it. but nevertheless a certain amount of structure is present, which we will shortly proceed to unravel.

First of all note its general appearance. You see a flat mass of clear jelly, very irregular in shape, " with sinuosities and jutting joints, like the outline of some island in a map," as Gosse aptly says. In the central part are seen a large number of very minute blackish granules, but round the edges it is clear and colourless. But even while you gaze upon it, you see that its form is ever changing; that never at; two successive moments is it of exactly , the same shape. Following these move- I ments for a little while, as they proceed without a moment's intermission, and apparently under no recognised rule or order, we see, in the graphic language of Mr. Gosse, that " the projections are obliterated or exaggerated;'the sinuosities are smoothed or deepened into gulfs,, or protruded into promontories; firths form here, capes there; but not by starts, but evenly, and with sufficient rapidity to be appreciable to the eye while under actual observation; though the alterations are more striking if you take your eye off the object for a few seconds,' and then look again." At times it seems to merge into the water wherein it lives, and almost fades out of sight. It will; frequently assume the appearance of a drawn-out line, and shortly afterwards its soft body is dragged forwards. It pushes out a " leg" from any point, according to the direction it desires to take. * These protrusions are known as pseudopodia, that is, " false feet." They can be produced at' any moment, but have no permanence, sinking back again into the protoplasm of the body when not required. Th» inner part of the creature consists of the granular matter, above mentioned, which may be seen flowing in different directions. Bound this is a clear envelope known as the " ectosarcj" which may escape observation unless it is carefully looked for with skilful manipulation of the light from the mirror. Amoeba was also described by the earlier zoologists as being without structure. But, as already stated, the vast improvement in the construction of lenses during recent years, has demonstarted that, so far as we know, no such thing as structureless protoplasm exists. Professor J. A. Thomson, describing the Infusorians, remarks that "Ehrenberg, who described them as ' perfect organisms,' and fancied he saw vessels, hearts, and other organs within them, was nearer the truth than those who reduce the singlecelled animals to the level of the white of egg." The distinction between " ectosarc' , and "endosarc" is clearly , marked in the Amoeba. The former is the firmer, slightly condensed external layer or film of protoplasm with which the "endosarc; or semi-fluid internal protoplasm, is in contact. In this respect it closely resembles an ordinary "cell,", composed of cell-wall and cell-contents. The coloured granular particles which we noticed in the specimen under examination, are diffused through the endosaro alone t and on them the hue and opacity of the body depend. The extreme central portion of the endosaro is of an almost watery consistency, for the granular particles may be seen moving quite freely upon one another every time the body changes its shape but its superficial portion is more viscid, and seems to graduate by insensible degrees into the firmer substance of the ectorsarc This latter is perfectly pellucid, and forms a kind of membranous investment to the endosarc. Yet it can scarcely be called a akin, for it does not possess such tenacity as to oppose the introduction of food particles at any point, or prevent the expulsion of effete matter. The structure I am endeavouring to describe to you is rather an important one, so that the following admirable account of it given by Professor Huxley will. I hope, make my ..• meaning perfectly clear —" Physically," he writes, " the ectosaro might be compared, to the wall of a soap-bubble, which, though fluid, has a certain viscosity, which not only enables its particles to bold together and form a continuous sheet, but permits a rod to be passed into or through the bubble without bursting it, the walls closing together and recovering their continuity as soon as the rod is drawn away." Apply these words to the Amoeba, and you will have an accurate idea of its external covering. In the granular mass a darker spot is always distinctly visible, whose form remains unchanged while the rest of the protoplasm is flowing all round it. This is the " Nucleus," which is essential to the life and reproduction of every veil. In the Amoeba it adheres to the inner 1 portion of the ectesarc, and projects from this into the cavity occupied by the eni dosarc. When seen at its best, it appears as a clear, flattened vesicle, containing a solid, spherical central mass, known as the inner nucleus, or " nucleolus. "* When we' come to consider the phenomena of reproduction in the Amoeba, we shall see what an important part the nucleus the bearer of the hereditary qualities. There is one species of Amoeba, described by Professor Weismann, which "lives in symbiosis, or partnership with a green alga, in the same manner as I described i when dealing wth Hydra viridis. ,Dr. > Weismann says that in the ZoologicalTnsti- ! tute of the University of Freiberg (at i which he occupies the chair of zoology) he I has a) living colony of these Amoebae, i which were sent to him from America. I He has made a careful study of them, '■ and is convinced that it is a true case of 1 symbiosis, because the algae yield oxygen 1 and food-stuffs which the Amoeba require and if the latter are kept in the dark. : away from the sunlight, the algae are unable to assimilate, and waste away and 1 disappear while their hosts also die from the doubts cause of lack of oxygen and lack of food. '"''.,'. In 'the three concluding articles of this I series we will consider the phenomena of reproduction,, sensation, and autrjtiott in L.tM>BWf*S>