still larger question of the primordial relation of living things to
the non-living world. Here is involved the possibility so strikingly
expressed many years ago by Tyndall in that eloquent passage in the
Belfast address, where he declared himself driven by an intellectual
necessity to cross the boundary line of the experimental evidence and
to discern in non-living matter, as he said, the promise and potency of
every form and quality of terrestrial life. This intellectual necessity
was created by a conviction of the continuity and consistency of
natural phenomena, which is almost inseparable from the scientific
attitude towards nature. But Tyndall's words stood after all for a
confession of faith, not for a statement of fact; and they soared far
above the _terra firma_ of the actual evidence. At the present day we
too may find ourselves logically driven to the view that living things
first arose as a product of non-living matter. We must fully recognize
the extraordinary progress that has been made by the chemist in the
artificial synthesis of compounds formerly known only as the direct
products of living protoplasm. But it must also be admitted that we are
still wholly without evidence of the origin of any living thing, at any
period of the earth's history, save from some other living thing; and
after more than two centuries Redi's aphorism _omne vivum e vivo_
retains to-day its full force. It is my impression therefore that the
time has not yet come when hypotheses regarding a different origin of
life can be considered as practically useful.

If I have the temerity to ask your attention to the fundamental
problem towards which all lines of biological inquiry sooner or later
lead us it is not with the delusion that I can contribute anything new
to the prolonged discussions and controversies to which it has given
rise. I desire only to indicate in what way it affects the practical
efforts of biologists to gain a better understanding of the living
organism, whether regarded as a group of existing phenomena or as a
product of the evolutionary process; and I shall speak of it, not in
any abstract or speculative way, but from the standpoint of the
working naturalist. The problem of which I speak is that of organic
mechanism and its relation to that of organic adaptation. How in
general are the phenomena of life related to those of the non-living
world? How far can we profitably employ the hypothesis that the living
body i