form, they have gone on developing ever since, from
the homogeneous to the heterogeneous, assuming ever more varied shapes,
till at last they have reached their present enormous variety of tree,
and shrub, and herb, and seaweed, of beast, and bird, and fish, and
creeping insect. Evolution throughout has been one and continuous, from
nebula to sun, from gas-cloud to planet, from early jelly-speck to man
or elephant. So at least evolutionists say--and of course they ought to
know most about it.

But evolution, according to the evolutionists, does not even stop here.
Psychology as well as biology has also its evolutionary explanation:
mind is concerned as truly as matter. If the bodies of animals are
evolved, their minds must be evolved likewise. Herbert Spencer and his
followers have been mainly instrumental in elucidating this aspect of
the case. They have shown, or they have tried to show (for I don't want
to dogmatise on the subject), how mind is gradually built up from the
simplest raw elements of sense and feeling; how emotions and intellect
slowly arise; how the action of the environment on the organism begets a
nervous system of ever greater and greater complexity, culminating at
last in the brain of a Newton, a Shakespeare, or a Mendelssohn. Step by
step, nerves have built themselves up out of the soft tissues as
channels of communication between part and part. Sense-organs of
extreme simplicity have first been formed on the outside of the body,
where it comes most into contact with external nature. Use and wont have
fashioned them through long ages into organs of taste and smell and
touch; pigment spots, sensitive to light or shade, have grown by
infinite gradations into the human eye or into the myriad facets of bee
and beetle; tremulous nerve-ends, responsive sympathetically to waves of
sound, have tuned themselves at last into a perfect gamut in the
developed ear of men and mammals. Meanwhile corresponding percipient
centres have grown up in the brain, so that the coloured picture flashed
by an external scene upon the eye is telegraphed from the sensitive
mirror of the retina, through the many-stranded cable of the optic
nerve, straight up to the appropriate headquarters in the thinking
brain. Stage by stage the continuous process has gone on unceasingly,
from the jelly-fish with its tiny black specks of eyes, through infinite
steps of progression, induced by ever-widening intercourse with the
outer world, to