The simplest form in which LIFE is manifested is in a viscid gelatinous
substance without colour or form, called _Protoplasm_. Wherever there is
life there is protoplasm. Protoplasm, as before remarked, lies just
under the bark in trees, and is the material from which the growth of
the wood and bark cells and fibres proceeds. Protoplasm, is also present
in the muscles and in the blood, and wherever growth is going on.
But protoplasm also exists by itself; or, more properly speaking, there
exist living creatures, both plant and animal, which are so simple in
structure, so low in organization, that they consist of nothing but a
speck of protoplasm. Such a creature is the microscopic _amoeba_.
Sometimes these little specks of protoplasm are surrounded with
beautifully formed "silicious shells--a skeleton of radiating _spiculae_
or crystal-clear concentric spheres of exquisite symmetry and
beauty.[1]" The simplest _amoeba_ however, has no definite form; but the
little mass moves about, expands and contracts, throws out projections
on one side and draws them in on the other. It exhibits irritability
when touched. It may be seen surrounding a tiny particle of food,
extracting nutriment from it and growing in size. Ultimately the little
body separates or splits up into two, each part thenceforth taking a
separate existence.
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