precise nature of the undertaking which Mr. Darwin has taken in hand;
that I should endeavour to show you what are the only methods by which
that undertaking can be brought to an issue, and to point out to you
how far the author of the work in question has satisfied those
conditions, how far he has not satisfied them, how far they are
satisfiable by man, and how far they are not satisfiable by man.

To-night, in taking up the first part of this question, I shall
endeavour to put before you a sort of broad notion of our knowledge of
the condition of the living world. There are many ways of doing this.
I might deal with it pictorially and graphically. Following the
example of Humboldt in his "Aspects of Nature", I might endeavour to
point out the infinite variety of organic life in every mode of its
existence, with reference to the variations of climate and the like;
and such an attempt would be fraught with interest to us all; but
considering the subject before us, such a course would not be that best
calculated to assist us. In an argument of this kind we must go
further and dig deeper into the matter; we must endeavour to look into
the foundations of living Nature, if I may so say, and discover the
principles involved in some of her most secret operations. I propose,
therefore, in the first place, to take some ordinary animal with which
you are all familiar, and, by easily comprehensible and obvious
examples drawn from it, to show what are the kind of problems which
living beings in general lay before us; and I shall then show you that
the same problems are laid open to us by all kinds of living beings.
But first, let me say in what sense I have used the words "organic
nature." In speaking of the causes which lead to our present knowledge
of organic nature, I have used it almost as an equivalent of the word
"living," and for this reason,--that in almost all living beings you
can distinguish several distinct portions set apart to do particular