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Updated: May 20, 2025
We actually do find colonies of unicellular animals much like amoeba, so that the muscle-cells and all other cells of the body may be compared to amoeba and other one-celled animals. But while in such unicellular creatures all functions are properties of the individual cell, among higher forms systems take the place of the protoplasm of the single cell.
Its earliest forms are unknown, but analogy suggests that as every living creature has developed from a single cell, so the earliest organisms upon the globe the germs from which all later life is supposed to have been evolved were tiny, unicellular masses of protoplasm, resembling the amoeba of to-day in the simplicity of their structure.
The Gastraea itself has originated from the simple multicellular vesicle, the Blastaea, and this in turn must have been evolved from the lowest circle of unicellular animals, to which we give the name of Protozoa. We have already considered the most important primitive type of these, the unicellular Amoeba, which is extremely instructive when compared with the human ovum.
So unstable is it that any disturbing influence will affect it. If two similar unicellular organisms are placed under different conditions they become unlike, since their unstable protoplasm is directly affected by the surrounding conditions. With higher animals the process is naturally a little more complicated; but here, too, they are easily understood as part of the function of the machine.
Bateson asks us to consider therefore whether all the divers types of life may not have been produced by the gradual unpacking of an original complexity in the primordial, probably unicellular forms, from which existing species and varieties have descended. Such a suggestion in the present writer's opinion is in one sense a truism and in another an absurdity.
Some impulse or tendency was latent or potential in the first unicellular life that rested not till it eventuated in each of these higher forms. Did any terrestrial or celestial calamity endanger the line of descent of any of the higher creatures?
On the other hand, the most marvellous displays of instinct are to be found not only in plants, but also in those lowest organisms of the simplest bodily form which are partly unicellular, and in respect of conscious intelligence stand far below the higher plants to which, indeed, any kind of deliberative faculty is commonly denied.
The previous chapters have taught us how the human body as a whole develops from the first simple rudiment, a single layer of cells. The whole human race owes its origin, like the individual man, to a simple cell. The unicellular stem-form of the race is reproduced daily in the unicellular embryonic stage of the individual.
It is typical of the course of the creative energy from the first unicellular life up to man, each succeeding stage flowing out of, and necessitated by, the preceding stage. How slowly and surely the circulatory system improved! From the cold-blooded animal to the warm-blooded is a great advance.
It not only leads the dance along our own line of descent from our remote ancestors it leads the dance along the long road of evolution from the first unicellular form in the dim palæozoic seas to the complex and highly specialized forms of our own day. The secret of this life force, or biotic energy, according to Professor Moore, is in the keeping of matter itself.
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