t all before you, and the
most I can do, or need do to-night, is to take up the principal points
and put them before you with such prominence as may subserve the
purposes of our present argument.

The method of the perpetuation of organic beings is of two kinds,--the
asexual and the sexual. In the first the perpetuation takes place from
and by a particular act of an individual organism, which sometimes may
not be classed as belonging to any sex at all. In the second case, it is
in consequence of the mutual action and interaction of certain portions
of the organisms of usually two distinct individuals,--the male and the
female. The cases of asexual perpetuation are by no means so common as
the cases of sexual perpetuation; and they are by no means so common in
the animal as in the vegetable world. You are all probably familiar with
the fact, as a matter of experience, that you can propagate plants
by means of what are called "cuttings;" for example, that by taking a
cutting from a geranium plant, and rearing it properly, by supplying it
with light and warmth and nourishment from the earth, it grows up
and takes the form of its parent, having all the properties and
peculiarities of the original plant.

Sometimes this process, which the gardener performs artificially, takes
place naturally; that is to say, a little bulb, or portion of the plant,
detaches itself, drops off, and becomes capable of growing as a separate
thing. That is the case with many bulbous plants, which throw off in
this way secondary bulbs, which are lodged in the ground and become
developed into plants. This is an asexual process, and from it results
the repetition or reproduction of the form of the original being from
which the bulb proceeds.

Among animals the same thing takes place. Among the lower forms of
animal life, the infusorial animalculae we have already spoken of throw
off certain portions, or break themselves up in various directions,
sometimes transversely or sometimes longitudinally; or they may give off
buds, which detach themselves and develop into their proper forms. There
is the common fresh-water Polype, for instance, which multiplies itself
in this way. Just in the same way as the gardener is able to multiply
and reproduce the peculiarities and characters of particular plants
by means of cuttings, so can the physiological experimentalist--as was
shown by the Abbe Trembley many years ago--so can he do the same thing
with many of