e stalk is very short and
very thick, the terminal divisions are very broad and flat, and one of
them is divided into two pieces.

I may say, therefore, that the sixth segment is like the others in plan,
but that it is modified in its details.

The first segment is like the others, so far as its ring is concerned,
and though its appendages differ from any of those yet examined in the
simplicity of their structure, parts corresponding with the stem and one
of the divisions of the appendages of the other segments can be readily
discerned in them.

Thus it appears that the lobster's tail is composed of a series of
segments which are fundamentally similar, though each presents peculiar
modifications of the plan common to all. But when I turn to the forepart
of the body I see, at first, nothing but a great shield-like shell,
called technically the "carapace," ending in front in a sharp spine, on
either side of which are the curious compound eyes, set upon the ends of
stout movable stalks. Behind these, on the under side of the body, are
two pairs of long feelers, or antennae, followed by six pairs of jaws
folded against one another over the mouth, and five pairs of legs, the
foremost of these being the great pinchers, or claws, of the lobster.

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