ture. As the different cells in
the multicellular mass became associated into groups for different
duties, the method of such division of labor was not alike in all
machines. A city in China and one in America are alike made up of
individuals, and the fundamental needs of the Chinaman and the American
are alike. But differences in industrial and political conditions have
produced different combinations and associations, so that Pekin is
wonderfully unlike New York. So in these early developing machines,
quite a variety of method of organization was adopted by the different
groups. Now as soon as any special type of organization was adopted by
any animal or plant, the principle of heredity transmitted the same kind
of organization to its descendants, and there thus arose lines of
descent differing from each other, each line having its own method of
organization. As we follow the history of each line the same thing is
repeated. We find that the representatives of each line again separate
into groups, each of which has acquired some new type of organization,
and there has thus been a constant divergence of these lines of descent
in an indefinite number of directions. The members of the different
lines of descent all show a fundamental likeness with each other since
they retain the fundamental characters of their common ancestor, but
they show also the differences which they have themselves acquired. And
thus the process is repeated over and over again. This history of the
growth of these different machines has thus been one of divergence from
common centres, and is to be diagrammatically expressed after the
fashion of a branching tree. The end of each branch represents the
highest state of perfection to which each line has been carried.

One other point in this history must be noted. As the development of the
complication of the machine progressed the possibility of further
progress has been constantly narrowed. When the history of these
machines began as a simple mass of cells, there was a possibility of an
almost endless variety of methods of organization. But as a distinct
type of organization was adopted by one and another line of descendants
all subsequent productions were limited through the law of heredity to
the general line of organization adopted by their ancestors. With each
age the further growth of such machines must consist in the further
development in the perfection of its parts, and not in the adoption of