rmined on the nature of the methods we are to pursue
and which only can lead to success, I must now turn to the consideration
of our knowledge of the nature of the processes which have resulted in
the present condition of organic nature.

Here, let me say at once, lest some of you misunderstand me, that I have
extremely little to report. The question of how the present condition of
organic nature came about, resolves itself into two questions. The first
is: How has organic or living matter commenced its existence? And the
second is: How has it been perpetuated? On the second question I shall
have more to say hereafter. But on the first one, what I now have to say
will be for the most part of a negative character.

If you consider what kind of evidence we can have upon this matter, it
will resolve itself into two kinds. We may have historical evidence and
we may have experimental evidence. It is, for example, conceivable, that
inasmuch as the hardened mud which forms a considerable portion of the
thickness of the earth's crust contains faithful records of the past
forms of life, and inasmuch as these differ more and more as we go
further down,--it is possible and conceivable that we might come to
some particular bed or stratum which should contain the remains of those
creatures with which organic life 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,