But is the amoeba really structureless? Probably it has an
exceedingly complex structure, but our microscopes and technique are
still too imperfect to show more than traces of it. Says Hertwig:
"Protoplasm is not a single chemical substance, however complicated,
but a mixture of many substances, which we must picture to ourselves
as finest particles united in a wonderfully complicated structure."
Truly protoplasm is, to borrow Mephistopheles' expression concerning
blood, a "quite peculiar juice." And the complexity of the nucleus
is far more evident than that of the protoplasm. Is protoplasm
itself the result of a long development? If so, out of what and how
did it develop? We cannot even guess. But the beginning of life may,
apparently must, have been indefinitely farther back than the
simplest now existing form. The study of the amoeba cannot fail to
raise a host of questions in the mind of any thoughtful man.

As we have here the animal reduced, so to speak, to lowest terms, it
may be well to examine a little more closely into its physiology and
compare it briefly with our own.

The amoeba eats food as we do, but the food is digested directly
in the internal protoplasm instead of in a stomach; and once
digested it diffuses to all parts of the cell; here it is built up
into compounds of a more complex structure, and forms an integral
part of the animal body. The dead food particle has been transformed
into living protoplasm, the continually repeated miracle of life.
But it does not remain long in this condition. In contact with the
oxygen from the air it is soon oxidized, burned up to furnish the
energy necessary for the motion and irritability of the body. We are
all of us low-temperature engines. The digestive function exists in