sion. Two
units now exist; the total mass immediately on division is
unaltered, but paths for the more abundant absorption of energy
are laid open.

The encystment of the protoplasm (occurring under conditions upon
which naturalists do not seem agreed[1]) is to all appearance
protective from an unfavourable environment, but it is often a
period of internal change as well, resulting in a segregation
within the mass of numerous small units, followed by a breakup of
the whole into these units. It is thus an extension of the basis
of supply, and in an impoverished medium, where unit of surface
is less active, is evidently the best means of preserving a
condition of progress.

Thus, in the organism which forms the basis of all modes of life,
a definite law of action is obeyed under various circumstances of
reaction with the available energy of its environment.

Similarly, in the case of the more complex leaf, we see, not only
in the phenomenon of growth, but in its extension in a flattened
form, and in the orientation of greatest surface towards the
source of energy, an attitude towards

[1] However, "In no way comparable with death." Weismann,
_Biological Memoirs_, p. 158.

68

available energy causative of accelerated transfer. There is
seemingly a principle at work, leading to the increase of organic
activity.

Many other examples might be adduced. The gastrula stage in the
development of embryos, where by invagination such an arrangement
of the multiplying cells is secured as to offer the greatest
possible surface consistent with a first division of labour; the
provision of cilia for drawing upon the energy supplies of the
medium; and more generally the specialisation of organs in the
higher developments of life, may alike be regarded as efforts of
the organism directed to the absorption of energy. When any
particular organ becomes unavailing in the obtainment of
supplies, the organ in the course of time becomes aborted or
disappears.[1] On the other hand, when a too ready and liberal
supply renders exertion and specialisation unnecessary, a similar
abortion of functionless organs takes place. This is seen in the
degraded members of certain parasites.

During certain epochs of geological history, the vegetable world
developed enormously; in response probably to liberal supplies of
carbon dioxide. A structural adaptation to the rich atmosphere
occurred, such as was calculated to cooperate in rapidly
consumi