n to himself, even in an imperfect manner, how it is possible
for a character possessed by some remote ancestor suddenly to reappear in
the offspring; how the effects of increased or decreased use of a limb can
be transmitted to the child; how the male sexual element can act not solely
on the ovule, but occasionally on the mother-form; how a limb can be
reproduced on the exact line of amputation, with neither too much nor too
little added; how the various modes of reproduction are connected, and so
forth. I am aware that my view is merely a provisional hypothesis or
speculation; but until a better one be advanced, it may be serviceable by
bringing together a multitude of facts which are at present left
disconnected by any efficient cause. As Whewell, the historian of the
inductive sciences, remarks:--"Hypotheses may often be of service to
science, when they involve a certain portion of incompleteness, and even of
error." Under this point of view I venture to advance the hypothesis of
Pangenesis, which {358} implies that the whole organisation, in the sense
of every separate atom or unit, reproduces itself. Hence ovules and
pollen-grains,--the fertilised seed or egg, as well as buds,--include and
consist of a multitude of germs thrown off from each separate atom of the
organism.

In the First Part I will enumerate as briefly as I can the groups of facts
which seem to demand connection; but certain subjects, not hitherto
discussed, must be treated at disproportionate length. In the Second Part
the hypothesis will be given; and we shall see, after considering how far
the necessary assumptions are in themselves improbable, whether it serves
to bring under a single point of view the various facts.

PART I.

Reproduction may be divided into two main classes, namely, sexual and
asexual. The latter is effected in many ways--by gemmation, that is by the
formation of buds of various kinds, and by fissiparous generation, that is
by spontaneous or artificial division. It is notorious that some of the
lower animals, when cut into many pieces, reproduce so many perfect
individuals: Lyonnet cut a Nais or freshwater worm into nearly forty
pieces, and these all reproduced perfect animals.[874] It is probable that
segmentation could be carried much further in some of the protozoa, and
with some of the lowest plants each cell will reproduce the parent-form.
Johannes Mueller thought that there was an important distinction between
gemmati