ty and diminution of fertility which is met with in ascending to
creatures of higher and higher development. Those relations in the
environment to which relations in the organism must correspond increase
in number and intensity as the life assumes a higher form. Perfect
correspondence would be perfect life.

_Growth, or Increase of Bulk_

Perhaps the widest and most familiar induction of biology is that
organisms grow. Under appropriate conditions increase of size takes
place in inorganic aggregates as well as in organic aggregates. Crystals
grow. Growth is indeed a concomitant of evolution. The several
conditions by which the phenomena of organic growth are governed,
conspiring and conflicting in endless ways and degrees, qualify more or
less differently each others' effects. Hence the following
generalisations must be taken as true on the average, or other things
equal:--

First, that growth being an integration with the organism of such
environing matters as are of like nature with the matters composing the
organism, its growth is dependent on the available supply of such
matters. Second, that the available supply of assimilable matters being
the same, and other conditions not dissimilar, the degree of growth
varies according to the surplus of nutrition over expenditure. Third,
that in the same organism the surplus of nutrition over expenditure is a
variable quantity; and that growth is unlimited or has a definite limit
according as the surplus does or does not progressively decrease,--a
proposition exemplified by the increasing growth of organisms that do
not expend force, and by the definitely limited growth of organisms that
expend much force. Fourth, that among organisms that are large expenders
of force, the size ultimately attained is, other things equal,
determined by the initial size. Fifth, that where the likeness of other
circumstances permits a comparison, the possible degree of growth
depends upon the degree of organisation: an inference testified to by
the larger forms among the various divisions and subdivisions of
organisms.

_Why Do Organisms Cease to Grow_

Why should not all organisms, when supplied with sufficient material,
continue to grow as long as they live? We have found that organisms are
mostly built up of compounds which are stores of force. These substances
being at once the materials for organic growth and the sources of
organic force, it follows, from the persistence of force,