term the sub-kingdom
'Coelenterata', would have grouped themselves around my type; had a
snail been chosen, the inhabitants of all univalve and bivalve, land and
water, shells, the lamp shells, the squids, and the sea-mat would have
gradually linked themselves on to it as members of the same sub-kingdom
of 'Mollusca'; and finally, starting from man, I should have been
compelled to admit first, the ape, the rat, the horse, the dog, into the
same class; and then the bird, the crocodile, the turtle, the frog, and
the fish, into the same sub-kingdom of 'Vertebrata'.

And if I had followed out all these various lines of classification
fully, I should discover in the end that there was no animal, either
recent or fossil, which did not at once fall into one or other of these
sub-kingdoms. In other words, every animal is organized upon one
or other of the five, or more, plans, whose existence renders our
classification possible. And so definitely and precisely marked is the
structure of each animal, that, in the present state of our knowledge,
there is not the least evidence to prove that a form, in the slightest
degree transitional between any of the two groups 'Vertebrata',
'Annulosa', 'Mollusca', and 'Coelenterata', either exists, or has
existed, during that period of the earth's history which is recorded by
the geologist. Nevertheless, you must not for a moment suppose,
because no such transitional forms are known, that the members of the
sub-kingdoms are disconnected from, or independent of, one another. On
the contrary, in their earliest condition they are all alike, and the
primordial germs of a man, a dog, a bird, a fish, a beetle, a snail, and
a polype are, in no essential structural respects, distinguishable.

In this broad sense, it may with truth be said, that all living animals,
and all those dead creations which geology reveals, are bound together
by an all-pervading unity of organization, of the same character, though
not equal in degree, to that which enables us to discern one and the
same plan amidst the twenty different segments of a lobster's body.
Truly it has been said, that to a clear eye the smallest fact is a
window through which the Infinite may be seen.

Turning from these purely morphological considerations, let us now
examine into the manner in which the attentive study of the lobster
impels us into other lines of research.

Lobsters are found in all the European seas; but on the opposite shores