oxidized or burnt. These particles immediately pass off as carbonic acid
gas and water vapor which are no longer parts of the flame. A fountain is
continually replenished by the water which is not-fountain, but which
becomes for the time a part of the graceful jet, falling out and away as
it leaves the fountain itself. Just so a living organism is an ever
changing, ever renewed, and ever destroyed mass of little particles--the
atoms of the inorganic world which combine and come to life for a time,
but which return inevitably to the world of lifeless things. This is one
of the most fundamental facts of biology. The independence of a living
thing like a human being or a crustacean is a product of the imagination.
How can we be independent of the environment when we are interlocked in so
many ways with inorganic nature? Our very substance with its energies has
been wrested from the environment; and as we, like all other living
things, must replenish our tissues as we wear out in the very act of
living, we cannot cease to maintain the closest possible relations with
the environment without surrendering our existence in the battle of life.

From the foregoing discussion, it will be evident, I am sure, that there
is ample justification for the biological dictum that a living individual
is a mechanism. Not only is the organism composed always of cell units
grouped mechanically in tissues and organs and organic systems; not only
are the operations which make up its life constant and regular under
similar conditions; not only is the whole creature mechanically connected
with the inorganic world; but above all the whole activity of a biological
individual is concerned necessarily and again mechanically with the
acquisition of materials endowed with energy, which materials and energy
are mechanically transformed into living matter and its life. Even though
an organism is so much more complex than a locomotive, and so plastic,
nevertheless, in so far as both are mechanisms, the conception of the
evolution of the former may be much more readily understood through a