er that when two spherules of olive-oil suspended in a mixture
of alcohol and water of the same density as the oil, are brought
together, they do not immediately unite. Something like a pellicle
appears to be formed around the drops, the rupture of which is
immediately followed by the coalescence of the globules into one.
There are organisms whose vital actions are almost as purely physical
as the coalescence of such drops of oil. They come into contact and
fuse themselves thus together. From such organisms to others a shade
higher, from these to others a shade higher still, and on through an
ever-ascending series, Mr. Spencer conducts his argument. There are
two obvious factors to be here taken into account--the creature and
the medium in which it lives, or, as it is often expressed, the
organism and its environment. Mr. Spencer's fundamental principle is,
that between these two factors there is incessant interaction. The
organism is played upon by the environment, and is modified to meet
the requirements of the environment. Life he defines to be 'a
continuous adjustment of internal relations to external relations.

In the lowest organisms we have a kind of tactual sense diffused over
the entire body; then, through impressions from without and their
corresponding adjustments, special portions of the surface become more
responsive to stimuli than others. The senses are nascent, the basis
of all of them being that simple tactual sense which the sage
Democritus recognised 2,300 years ago as their common progenitor. The
action of light, in the first instance, appears to be a mere
disturbance of the chemical processes in the animal organism, similar
to that which occurs in the leaves of plants. By degrees the action
becomes localised in a few pigment-cells, more sensitive to light than
the surrounding tissue. The eye is incipient. At first it is merely
capable of revealing differences of light and shade produced by bodies
close at hand. Followed, as the interception of the light commonly
is, by the contact of the closely adjacent opaque body, sight in this
condition becomes a kind of 'anticipatory touch.' The adjustment
continues; a slight bulging out of the epidermis over the
pigment-granules supervenes. A lens is incipient, and, through the
operation of infinite adjustments, at length reaches the perfection
that it displays in the hawk and eagle. So of the other senses; they
are special differentiations of