CHAPTER III.
A garden wall, and its traces of past life—Not a breath perishes—A bit of dry moss and its inhabitants—The “Wheel-bearers”—Resuscitation of Rotifers: drowned into life—Current belief that animals can be revived after complete desiccation—Experiments contradicting the belief—Spallanzani’s testimony—Value of biology as a means of culture—Classification of animals: the five great types—Criticism of Cuvier’s arrangement.
Pleasant, both to eye and mind, is an old garden wall, dark with age, gray with lichens, green with mosses of beautiful hues and fairy elegance of form: a wall shutting in some sequestered home, far from “the din of murmurous cities vast:” a home where, as we fondly, foolishly think, Life must needs throb placidly, and all its tragedies and pettinesses be unknown. As we pass alongside this wall, the sight of the overhanging branches suggests an image of some charming nook; or our thoughts wander about the wall itself, calling up the years during which it has been warmed by the sun, chilled by the night airs and the dews, and dashed against by the wild winds of March: all of which have made it quite another wall from what it was when the trowel first settled its bricks. The old wall has a past, a life, a story; as Wordsworth finely says of the mountain, it is “familiar with forgotten years.” Not only are there obvious traces of age in the crumbling mortar and the battered brick, but there are traces, not obvious, except to the inner eye, left by every ray of light, every raindrop, every gust. Nothing perishes. In the wondrous metamorphosis momently going on everywhere in the universe, there is change, but no loss.
Lest you should imagine this to be poetry, and not science, I will touch on the evidence that every beam of light, or every breath of air, which falls upon an object, permanently affects it. In photography we see the effect of light very strikingly exhibited; but perhaps you will object that this proves nothing more than that light acts upon an iodized surface. Yet in truth light acts upon, and more or less alters, the structure of every object on which it falls. Nor is this all. If a wafer be laid on a surface of polished metal, which is then breathed upon, and if, when the moisture of the breath has evaporated, the wafer be shaken off, we shall find that the whole polished surface is not as it was before, although our senses can detect no difference; for if we breathe again upon it, the surface will be moist everywhere except on the spot previously sheltered by the wafer, which will now appear as a spectral image on the surface. Again and again we breathe, and the moisture evaporates, but still the spectral wafer reappears. This experiment succeeds after a lapse of many months, if the metal be carefully put aside where its surface cannot be disturbed. If a sheet of paper, on which a key has been laid, be exposed for some minutes to the sunshine, and then instantaneously viewed in the dark, the key being removed, a fading spectre of the key will be visible. Let this paper be put aside for many months where nothing can disturb it, and then in darkness be laid on a plate of hot metal, the spectre of the key will again appear. In the case of bodies more highly phosphorescent than paper, the spectres of many different objects which may have been laid on in succession will, on warming, emerge in their proper order.[8]
This is equally true of our bodies, and our minds. We are involved in the universal metamorphosis. Nothing leaves us wholly as it found us. Every man we meet, every book we read, every picture or landscape we see, every word or tone we hear, mingles with our being and modifies it. There are cases on record of ignorant women, in states of insanity, uttering Greek and Hebrew phrases, which in past years they had heard their masters utter, without of course comprehending them. These tones had long been forgotten: the traces were so faint that under ordinary conditions they were invisible; but the traces were there, and in the intense light of cerebral excitement they started into prominence, just as the spectral image of the key started into sight on the application of heat. It is thus with all the influences to which we are subjected.
If a garden wall can lead our vagabond thoughts into such speculations as these, surely it may also furnish us with matter for our Studies in Animal Life? Those patches of moss must be colonies. Suppose we examine them? I pull away a small bit, which is so dry that the dust crumbles at a touch; this may be wrapped in a piece of paper—dirt and all—and carried home. Get the microscope ready, and now attend.
I moisten a fragment of this moss with distilled water. Any water will do as well, but the use of distilled water prevents your supposing that the animals you are about to watch were brought in it, and were not already in the moss. I now squeeze the bit between my fingers, and a drop of the contained water—somewhat turbid with dirt—falls on the glass slide, which we may now put on the microscope stage. A rapid survey assures us that there is no animal visible. The moss is squeezed again; and this time little yellowish bodies of an irregular oval are noticeable among the particles of dust and moss. Watch one of these, and presently you will observe a slow bulging at one end, and then a bulging at the other end. The oval has elongated itself into a form not unlike that of a fat caterpillar, except that there is a tapering at one end. Now a forked tail is visible; this fixes on to the glass, while the body sways to and fro. Now the head is drawn in—as if it were swallowed—and, suddenly, in its place are unfolded two broad membranes, having each a circle of waving cilia. The lifeless oval has become a living animal! You have assisted at a resuscitation, not from death by drowning, but by drying: the animal has been drowned into life! The unfolded membranes, with their cilia, have so much the appearance of wheels that the name of “Wheel-bearer” (Rotifera) or “Wheel Animalcule” has been given to the animal.
The Rotifera (also—and more correctly—called Rotatoria) form an interesting study. Let us glance at their organization:—
Fig. 16.