It looks, at first, a little hopeless to attempt to find in this complex
mass a series of rings, each with its pair of appendages, such as I
have shown you in the abdomen, and yet it is not difficult to
demonstrate their existence. Strip off the legs, and you will find that
each pair is attached to a very definite segment of the under wall of
the body; but these segments, instead of being the lower parts of free
rings, as in the tail, are such parts of rings which are all solidly
united and bound together; and the like is true of the jaws, the
feelers, and the eye-stalks, every pair of which is borne upon its own
special segment. Thus the conclusion is gradually forced upon us, that
the body of the lobster is composed of as many rings as there are pairs
of appendages, namely, twenty in all, but that the six hindmost rings
remain free and movable, while the fourteen front rings become firmly
soldered together, their backs forming one continuous shield--the
carapace.

Unity of plan, diversity in execution, is the lesson taught by the study
of the rings of the body, and the same instruction is given still more
emphatically by the appendages. If I examine the outermost jaw I find
it consists of three distinct portions, an inner, a middle, and an
outer, mounted upon a common stem; and if I compare this jaw with the
legs behind it, or the jaws in front of it, I find it quite easy to
see, that, in the legs, it is the part of the appendage which
corresponds with the inner division, which becomes modified into what we
know familiarly as the "leg," while the middle division disappears, and
the outer division is hidden under the carapace. Nor is it more
difficult to discern that, in the appendages of the tail, the middle
division appears again and the outer vanishes; while, on the other hand,
in the foremost jaw, the so-called mandible, the inner division only is
left; and, in the same way, the parts of the feelers and of the