reproducing by gemmation. Mr. Darwin must evidently admit
this, since he says: "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_."[218]

Moreover, these gemmules are supposed to tend to aggregate themselves, and
to reproduce in certain definite relations to other gemmules. Thus, when
the foot of an eft is cut off, its reproduction is explained by Mr. Darwin
as resulting from the aggregation of those floating gemmules which come
next in order to those of the cut surface, and the successive aggregations
of the other kinds of gemmules which come after in regular order. Also, the
most ordinary processes of repair are similarly accounted for, and the
successive development of similar parts and organs in creatures in which
such complex evolutions occur is explained in the same way, by the
independent action of separate gemmules.

In order that each living creature may be thus furnished, the number of
such gemmules in each must be inconceivably great. Mr. Darwin says:[219]
"In a highly organized and complex animal, the gemmules thrown off from
each different cell or unit throughout the body must be inconceivably
numerous and minute. Each unit of each part, as it changes during
development--and we know that some insects undergo at least twenty {210}
metamorphoses--must throw off its gemmules. All organic beings, moreover,
include many dormant gemmules derived from their grandparents and more
remote progenitors, but not from all their progenitors. These _almost
infinitely numerous_ and minute gemmules must be included in each bud,
ovule, spermatozoon, and pollen grain." We have seen also that in certain
cases a similar multitude of gemmules must be included also in every
considerable part of the whole body of each organism, but where are we to
stop? There must be gemmules not only from every organ, but from every
component part of such organ, from every subdivision of such component
part, and from every cell, thread, or fibre entering into the composition
of such subdivision. Moreover, not only from all these, but from each and
every successive stage of the evolution and development of such
successively more and more elementary parts. At the first glance this new
atomic theory has charms from its apparent simplicity, but the attempt thus
to follow it out into