living_ protein--one of those minute microscopic living things which
throng our pools, and are known as Infusoria--such a creature, for
instance, as an Euglena, and place it in our vessel of water. It is a
round mass provided with a long filament, and except in this peculiarity
of shape, presents no appreciable physical or chemical difference
whereby it might be distinguished from the particle of dead protein.

But the difference in the phaenomena to which it will give rise is
immense: in the first place it will develop a vast quantity of physical
force--cleaving the water in all directions with considerable rapidity
by means of the vibrations of the long filament or cilium.

Nor is the amount of chemical energy which the little creature possesses
less striking. It is a perfect laboratory in itself, and it will act and
react upon the water and the matters contained therein; converting them
into new compounds resembling its own substance, and, at the same time,
giving up portions of its own substance which have become effete.

Furthermore, the Euglena will increase in size; but this increase is by
no means unlimited, as the increase of a crystal might be. After it has
grown to a certain extent it divides, and each portion assumes the form
of the original, and proceeds to repeat the process of growth and
division.

Nor is this all. For after a series of such divisions and subdivisions,
these minute points assume a totally new form, lose their long
tails--round themselves, and secrete a sort of envelope or box, in which
they remain shut up for a time, eventually to resume, directly or
indirectly, their primitive mode of existence.

Now, so far as we know, there is no natural limit to the existence of
the Euglena, or of any other living germ. A living species once launched
into existence tends to live for ever.

Consider how widely different this living particle is from the dead
atoms with which the physicist and chemist have to do!

The particle of gold falls to the bottom and rests--the particle of dead
protein decomposes and disappears--it also rests: but the _living_
protein mass neither tends to exhaustion of its forces nor to any
permanency of form, but is essentially distinguished as a disturber of
equilibrium so far as force is concerned,--as undergoing continual
metamorphosis and change, in point of form.

Tendency to equilibrium of force and to permanency of form then, are the
characters of that portion of