substances--water, carbonic acid, and ammonia--are present together with
appropriate conditions; it is said that they will combine to form a
gummy transparent matter, which is called _protoplasm_. This protoplasm
may be found in small shapeless lumps, or it may be found enclosed in
cells, and in various beautifully shaped coverings, and it is also found
in the blood, and in all growing parts or organs of all animals and
plants of every kind whatsoever.

Protoplasm, then, is the physical basis of life. Simple, uniform,
shapeless protoplasm, combined out of the substances just named, first
came into existence; and as, however simple or shapeless, it always
exhibits the property of life, it can henceforth grow and develop from
simpler to ever increasingly complex forms, without any help but that of
surrounding circumstances--the secondary causes which we see in
operation around us.

If some readers should say they have never seen _protoplasm_, I may
remind them where every one has, at some time or another, met with it.
If you cut a stick of new wood from a hedge, and peel off the young
bark, you know that the bark comes off easily and entire, leaving a
clean white wand of wood in your hand; but the wand feels sticky all
over. This sticky stuff is nothing more than transparent growing
protoplasm, which lies close under the inner bark.

At first, the materialist holds, protoplasm appeared in very simple
forms, just such as can still be found within the sea, and in ponds. But
the lower organized forms of life are extremely unstable, and a
different _environment_ will always tend to evoke continuous small
changes, so that there may be advance in forms of all kinds. For if by
chance[1] some creature exhibits a variation which is favourable to it