Some have regarded the cell as a crystal; they see the crystal forming, by the accumulation of atoms, into a fixed form, under the influence of an “inner life;” and, advancing but a step, they regard the cell as the result of an increased exercise of the physical influences.[253] We have referred crystalline form to certain magnetic conditions; and it is evident that the atomic cell is influenced by similar forces; but if we place a crystal in its natural fluid, though it increases in size, it never alters in form: whereas, if we examine a cell in its natural position, it gives indications of motion, it produces other cells, and we have a development of organs which are in no respect the same in form as the original. From a vesicle floating invisible to the unaided human sense in its womb of fluid, is produced a plant possessing strange powers, or an animal gifted with volition. The idea, that two kinds of polarity—light on one side, and gravitation on the other—produce the two peculiar developments of roots and branches, can only be regarded as one of those fanciful analogies which prove more imagination than philosophy.[254]
The conditions are, however, most curious; they deserve very attentive study; but in examining the phenomena, the safest course is to allow the effects as they arise to interpret to us, and not admit the love of hypothesis to lead us into bewildering analogies; or uncertain phenomena to betray us to hasty inferences. It is of this evil that Bacon speaks, in his “Advancement of Learning.” He says:—
“The root of this error, as of all others, is this, that men, in their contemplations of nature, are accustomed to make too timely a departure, and too remote a recess from experience and particulars, and have yielded and resigned themselves over to the fumes of their own fancies and popular argumentations.”
Without venturing, therefore, to speculate on the origin of the primitive cell, or unit of organic life, which involves the problem of the metamorphosis of a rude mass—the primitive transformation of the rudimentary atoms into organic form,—we must admit that the highly organized plant or animal is but an aggregation of cells; their arrangement being dependent upon certain properties peculiar to them, and the exercise of forces such as we have been studying,—all of which appear to act externally to the plant or animal itself.
Experiments have been brought forward, in which it appeared that, after all organization which could by any possibility have existed, had been destroyed by the action of fire, solutions of flint and metallic salts, have, under the influence of electric currents, exhibited signs of organic formations, and that, indeed, insects—a species of acari—have been developed in them. The experiments were said to have been made with care, and many precautions taken to shut out all chances of any error, but not all the precautions required in a matter of such exceeding delicacy; and we are bound not to receive the evidence afforded as the true expression of a fact without much further investigation. All experience,—setting aside the experiment named,—is against the supposition that pounded or dissolved flint could by any artificial means be awakened into life. Ova may have been conveyed into the vessels which contained the solutions under experiment; and in due time, although possibly quickened by electric excitation, the animals—the most common of insects—came into existence.[255]
The rapid growth of confervæ upon water has often been brought forward as evidence of a spontaneous generation, or the conversion of inorganic elements into organic forms; but it has been most satisfactorily proved that the germ must be present, otherwise no evidence of anything like organization will be developed. All the conditions required for the production of vegetable life appear to show, that it is quite impossible for any kind of plant, even the very lowest in the scale, to be formed in any other way than from an embryo in which are contained the elements necessary for it, and the arrangements required for the various processes which are connected with its vitality.
The earth is now covered with vegetable life, but there must have existed a time when “darkness was upon the face of the deep,” and organization had not yet commenced tracing its lovely net-work of cells upon the bare surface of the ocean-buried rock. At length the mystery of organic creation began: into this science dares not penetrate, but it is privileged to begin its search a little beyond this point, and we are enabled to trace the progress of organic development through a chain of interesting results which are constantly recurring.
If we take some water, rising from a subterranean spring, and expose it to sunshine, we shall see, after a few days, a curious formation of bubbles, and the gradual accumulation of green matter. At first we cannot detect any marks of organization—it appears a slimy cloud of an irregular and undetermined form. It slowly aggregates, and forms a sort of mat over the surface, which at the same time assumes a darker green colour. Careful examination will now show the original corpuscles involved in a net-work formed by slender threads, which are tubes of circulation, and may be traced from small points which we must regard as the compound atom, the vegetable unit. We must not forget, here, that we have to deal with four chemical elements,—oxygen, hydrogen, carbon, and nitrogen, which compose the world of organized forms, and that the water affords us the two first as its constituents, gives us carbon in the form of carbonic acid dissolved in it, and that nitrogen is in the air surrounding it, and frequently mixed with it also.
Under the influence of sunshine, we have now seen these elements uniting into a mysterious bond, and the result is the formation of a cellular tissue, which possesses many of the functions of the noblest specimens of vegetable growth. But let us examine the progress. The bare surface of a rock rises above the waters covered over with this green slime, a mere veil of delicate net-work, which, drying off, leaves no perceptible trace behind it; but the basis of a mighty growth is there, and under solar influence, in the process of time, other changes occur.
After a period, if we examine the rock, we shall find upon its face little coloured cups or lines with small hard discs. These, at first sight, would not be taken for plants, but on close examination they will be found to be lichens. These minute vegetables shed their seed and die, and from their own remains a more numerous crop springs into life. After a few of these changes, a sufficient depth of soil is formed, upon which mosses begin to develope themselves, and give to the stone a second time a faint tint of green, a mere film still, but indicating the presence of a beautiful class of plants, which, under the microscope, exhibit in their leaves and flowers many points of singular elegance. These mosses, like the lichens, decaying, increase the film of soil, and others of a larger growth supply their places, and run themselves the same round of growth and decay. By and by, funguses of various kinds mingle their little globes and umbrella-like forms. Season after season plants, perish and add to the soil, which is at the same time increased in depth by the disintegration of the rock over which it is laid, the cohesion of particles being broken up by the operations of vegetable life. The minute seeds of the ferns floating on the breeze, now find a sufficient depth of earth for germination, and their beautiful fronds, eventually, wave in loveliness to the passing winds.