the divisions are constructed upon the same plan. But now let us
consider the sixth division. It is similar to, and yet different from,
the others. The ring is essentially the same as in the other divisions;
but the appendages look at first as if they were very different; and
yet when we regard them closely, what do we find? A stalk and two
terminal divisions, exactly as in the others, but the 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.