began upon the earth. And if we did so, and if such forms of organic
life were preservable, we should have what I would call historical
evidence of the mode in which organic life began upon this planet. Many
persons will tell you, and indeed you will find it stated in many works
on geology, that this has been done, and that we really possess such a
record; there are some who imagine that the earliest forms of life of
which we have as yet discovered any record, are in truth the forms in
which animal life began upon the globe. The grounds on which they base
that supposition are these:--That if you go through the enormous
thickness of the earth's crust and get down to the older rocks, the
higher vertebrate animals--the quadrupeds, birds, and fishes--cease to
be found; beneath them you find only the invertebrate animals; and in
the deepest and lowest rocks those remains become scantier and
scantier, not in any very gradual progression, however, until, at
length, in what are supposed to be the oldest rocks, the animal remains
which are found are almost always confined to four forms--'Oldhamia',
whose precise nature is not known, whether plant or animal; 'Lingula',
a kind of mollusc; 'Trilobites', a crustacean animal, having the same
essential plan of construction, though differing in many details from a
lobster or crab; and Hymenocaris, which is also a crustacean. So that
you have all the 'Fauna' reduced, at this period, to four forms: one a
kind of animal or plant that we know nothing about, and three undoubted
animals--two crustaceans and one mollusc.

I think, considering the organization of these mollusca and crustacea,
and looking at their very complex nature, that it does indeed require a
very strong imagination to conceive that these were the first created
of all living things. And you must take into consideration the fact
that we have not the slightest proof that these which we call the
oldest beds are really so: I repeat, we have not the slightest proof of