lel
relation between the lives of the units and the life of the group is
shown us in _Uroglena_ and _Syncrypta_. From these first stages upwards,
may be traced through successively higher types, an increasing
subordination of the units to the aggregate; though still a
subordination leaving to them conspicuous amounts of individual
activity. Joining which facts with the phenomena presented by the
cell-multiplication and aggregation of every unfolding germ, naturalists
are now accepting the conclusion that by this process of composition
from _Protozoa_, were formed all classes of the _Metazoa_[50]--(as
animals formed by this compounding are now called); and that in a
similar way from _Protophyta_, were formed all classes of what I suppose
will be called _Metaphyta_, though the word does not yet seem to have
become current.

And now what is the general meaning of these truths, taken in connexion
with the conclusion reached in the last section. It is that this
universal trait of the _Metazoa_ and _Metaphyta_, must be ascribed to
the primitive action and re-action between the organism and its medium.
The operation of those forces which produced the primary differentiation
of outer from inner in early minute masses of protoplasm, pre-determined
this universal cell-structure of all embryos, plant and animal, and the
consequent cell-composition of adult forms arising from them. How
unavoidable is this implication, will be seen on carrying further an
illustration already used--that of the shingle-covered shore, the
pebbles on which, while being in some cases selected, have been in all
cases rounded and smoothed. Suppose a bed of such shingle to be, as we
often see it, solidified, along with interfused material, into a
conglomerate. What in such case must be considered as the chief trait of
such conglomerate; or rather--what must we regard as the chief cause of
its distinctive characters? Evidently the action of the sea. Without the
breakers, no pebbles; without the pebbles, no conglomerate. Similarly
then, in the absence of that action of the medium by which was effected
the differentiation of outer from inner in those microscopic portions of
protoplasm constituting the earliest and simplest animals and plants,
there could not have existed this cardinal trait of composition which
all the higher animals and plants show us.

So that, active as has been the part played by natural selection, alike
in modifying and moulding the ori