istinct or
independent character, and therefore calculated to display the
additional force which they acquire from their cumulative nature.

I.

THE ARGUMENT FROM CLASSIFICATION.

I shall first take the argument from classification. Naturalists find
that all species of plants and animals present among themselves
structural affinities. According as these structural affinities are more
or less pronounced, the various species are classified under genera,
orders, families, classes, sub-kingdoms, and kingdoms. Now in such a
classification it is found impossible to place all the species in a
linear series, according to the grade of their organization. For
instance, we cannot say that a wolf is more highly organized than a fox
or a jackal; we can only say that the specific points wherein it
differs from these animals are without significance as proving the one
type to be more highly organized than the others. But of course in many
cases, and especially in the cases of the larger divisions, it is often
possible to say--The members in this division are more highly organized
than are the members in that division. Our system of classification
therefore may be likened to a tree, in which a short trunk may be taken
to represent the lowest organisms which cannot properly be termed either
plants or animals. This short trunk soon separates into two large
trunks, one of which represents the vegetable and the other the animal
kingdom. Each of these trunks then gives off large branches signifying
classes, and these give off smaller, but more numerous branches,
signifying families, which ramify again into orders, genera, and finally
into the leaves, which may be taken to represent species. Now, in such
a representative tree of life, the height of any branch from the ground
may be taken to indicate the grade of organization which the leaves, or
species, present; so that, if we picture to ourselves such a tree, we
will understand that while there is a general advance of organization
from below upwards, there are numberless slight variations in this
respect between leaves growing even on the same branch; but in a still
greater number of cases, leaves growing on the same branch are growing
on the same level--that is, although they represent different species,
it cannot be said that one is more highly organized than the other. Now,
this tree-like arrangement of specific organisms in nature is an
arrangement for which Mr. Darwin is no