hese organisms no doubt reproduce themselves by germs of extreme
minuteness, relatively to their own minute size. Hence the difficulty,
which at first appears insurmountable, of believing in the existence of
gemmules so numerous and so small as they must be according to our
hypothesis, has really little weight.

The cells or units of the body are generally admitted by physiologists to
be autonomous, like the buds on a tree, but in a less degree. I go one step
further and assume that they throw off reproductive gemmules. Thus an
animal does not, as a whole, generate its kind through the sole agency of
the reproductive system, but each separate cell generates its kind. It has
often been said by naturalists that each cell of a plant has the actual or
potential capacity of reproducing the whole plant; but it has this power
only in virtue of containing gemmules derived from every part. If our
hypothesis be provisionally accepted, we must look at all the forms of
asexual reproduction, whether occurring at maturity or as in the case of
alternate generation during youth, as fundamentally the same, and dependent
on the mutual aggregation and multiplication of the gemmules. The regrowth
of an amputated limb or the healing of a wound is the same process
partially carried out. Sexual generation differs in some important
respects, chiefly, as it would appear, in an insufficient number of
gemmules being aggregated within the separate sexual elements, and probably
in the presence of certain primordial cells. The development of each being,
including all the {404} forms of metamorphosis and metagenesis, as well as
the so-called growth of the higher animals, in which structure changes
though not in a striking manner, depends on the presence of gemmules thrown
off at each period of life, and on their development, at a corresponding
period, in union with preceding cells. Such cells may be said to be
fertilised by the gemmules which come next in the order of development.
Thus the ordinary act of impregnation and the development of each being are
closely analogous processes. The child, strictly speaking, does not grow
into the man, but includes germs which slowly and successively become
developed and form the man. In the child, as well as in the adult, each
part generates the same part for the next generation. Inheritance must be
looked at as merely a form of growth, like the self-division of a
lowly-organised unicellular plant. Reversion depe