But you will observe one remarkable circumstance, that, up to this
point, the question of the life of these organisms has not come under
consideration. Morphology and distribution might be studied almost as
well, if animals and plants were a peculiar kind of crystals, and
possessed none of those functions which distinguish living beings so
remarkably. But the facts of morphology and distribution have to be
accounted for, and the science, whose aim it is to account for them, is
Physiology.

Let us return to our lobster once more. If we watched the creature in
its native element, we should see it climbing actively the submerged
rocks, among which it delights to live, by means of its strong legs; or
swimming by powerful strokes of its great tail, the appendages of whose
sixth joint are spread out into a broad fan-like propeller: seize it,
and it will show you that its great claws are no mean weapons of
offence; suspend a piece of carrion among its haunts, and it will
greedily devour it, tearing and crushing the flesh by means of its
multitudinous jaws.

Suppose that we had known nothing of the lobster but as an inert mass,
an organic crystal, if I may use the phrase, and that we could suddenly
see it exerting all these powers, what wonderful new ideas and new
questions would arise in our minds! The great new question would be,
"How does all this take place?" the chief new idea would be, the idea
of adaptation to purpose,--the notion, that the constituents of animal
bodies are not mere unconnected parts, but organs working together to
an end. Let us consider the tail of the lobster again from this point
of view. Morphology has taught us that it is a series of segments
composed of homologous parts, which undergo various