complex is everywhere evolved out of the simple. Every animal has at
first the form of an egg, and every animal and every organic part, in
reaching its adult state, passes through conditions common to other
animals and other adult parts; and this leads me to another point. I
have hitherto spoken as if the lobster were alone in the world, but, as
I need hardly remind you, there are myriads of other animal organisms.
Of these, some, such as men, horses, birds, fishes, snails, slugs,
oysters, corals, and sponges, are not in the least like the 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