distinctness may be called cell-gemmules, or, as the cellular
theory is not fully established, simply gemmules. They are supposed to be
transmitted from the parents to the offspring, and are generally developed
in the generation which immediately succeeds, but are often transmitted in
a dormant state during many generations and are then developed. Their
development is supposed to depend on their union with other partially
developed cells or gemmules which precede them in the regular course of
growth. Why I use the term union, will be seen when we discuss the direct
action of pollen on the tissues of the mother-plant. Gemmules are supposed
to be thrown off by every cell or unit, not only during the adult state,
but during all the stages of development. Lastly, I assume that the
gemmules in their dormant state have a mutual affinity for each other,
leading to their aggregation either into buds or into the sexual elements.
Hence, speaking strictly, it is not the reproductive elements, nor the
buds, which generate new organisms, but the cells themselves throughout the
body. These assumptions constitute the provisional hypothesis which I have
called Pangenesis. Nearly {375} similar views have been propounded, as I
find, by other authors, more especially by Mr. Herbert Spencer;[902] but
they are here modified and amplified.

{376}

Before proceeding to show, firstly, how far these assumptions are in
themselves probable, and secondly, how far they connect and explain the
various groups of facts with which we are concerned, it may be useful to
give an illustration of the hypothesis. If one of the simplest Protozoa be
formed, as appears under the microscope, of a small mass of homogeneous
gelatinous matter, a minute atom thrown off from any part and nourished
under favourable circumstances would naturally reproduce the whole; but if
the upper and lower surfaces were to differ in texture from the central
portion, then all three parts would have to throw off atoms or gemmules,
which when aggregated by mutual affinity would form either buds or the
sexual elements. Precisely the same view may be extended to one of the
higher animals; although in this case many thousand gemmules must be thrown
off from the various parts of the body. Now, when the leg, for instance, of
a salamander is cut off, a slight crust forms over the wound, and beneath
this crust the uninjured cells or units of bone, muscle, nerves, &c., are
supposed to unite w