lobster. But
other animals, though they may differ a good deal from the lobster, are
yet either very like it, or are like something that is like it. The cray
fish, the rock lobster, and the prawn, and the shrimp, for example,
however different, are yet so like lobsters, that a child would group
them as of the lobster kind, in contradistinction to snails and slugs;
and these last again would form a kind by themselves, in
contradistinction to cows, horses, and sheep, the cattle kind.

But this spontaneous grouping into "kinds" is the first essay of the
human mind at classification, or the calling by a common name of those
things that are alike, and the arranging them in such a manner as best
to suggest the sum of their likenesses and unlikenesses to other things.

Those kinds which include no other subdivisions than the sexes, or
various breeds, are called, in technical language, species. The English
lobster is a species, our cray fish is another, our prawn is another. In
other countries, however, there are lobsters, cray fish, and prawns,
very like ours, and yet presenting sufficient differences to deserve
distinction. Naturalists, therefore, express this resemblance and this
diversity by grouping them as distinct species of the same "genus." But
the lobster and the cray fish, though belonging to distinct genera, have
many features in common, and hence are grouped together in an assemblage
which is called a family. More distant resemblances connect the lobster
with the prawn and the crab, which are expressed by putting all these
into the same order. Again, more remote, but still very definite,
resemblances unite the lobster with the woodlouse, the king crab, the
water-flea, and the barnacle, and separate them from all other animals;
whence they collectively constitute the larger group, or class,
_Crustacea_. But the _Crustacea_ exhibit many peculiar features in
common with insects, spiders, and centipedes, so that these are grouped
into the still larger assemblage or "province" _Articulata_; and,
finally, the relations which these have to worms and other lower
animals, are expressed by combining the whole vast aggregate into the
sub-kingdom of _Annulosa_.

If I had worked my way from a sponge instead of a lobster, I should have
found it associated, by like ties, with a great number of other animals
into the sub-kingdom _Protozoa_; if I had selected a fresh-water polype
or a coral, the members of what naturalists term