etable world. Naturally, therefore, biologists enamored of
clean-cut concepts have regarded the distinction between the two
kingdoms as artificial. They would be right, if definition in this case
must be made, as in the mathematical and physical sciences, according to
certain statical attributes which belong to the object defined and are
not found in any other. Very different, in our opinion, is the kind of
definition which befits the sciences of life. There is no manifestation
of life which does not contain, in a rudimentary state--either latent or
potential,--the essential characters of most other manifestations. The
difference is in the proportions. But this very difference of proportion
will suffice to define the group, if we can establish that it is not
accidental, and that the group as it evolves, tends more and more to
emphasize these particular characters. In a word, _the group must not be
defined by the possession of certain characters, but by its tendency to
emphasize them_. From this point of view, taking tendencies rather than
states into account, we find that vegetables and animals may be
precisely defined and distinguished, and that they correspond to two
divergent developments of life.

This divergence is shown, first, in the method of alimentation. We know
that the vegetable derives directly from the air and water and soil the
elements necessary to maintain life, especially carbon and nitrogen,
which it takes in mineral form. The animal, on the contrary, cannot
assimilate these elements unless they have already been fixed for it in
organic substances by plants, or by animals which directly or indirectly
owe them to plants; so that ultimately the vegetable nourishes the
animal. True, this law allows of many exceptions among vegetables. We do
not hesitate to class amongst vegetables the Drosera, the Dionaea, the
Pinguicula, which are insectivorous plants. On the other hand, the
fungi, which occupy so considerable a place in the vegetable world, feed
like animals: whether they are ferments, saprophytes or parasites, it is
to already formed organic substances that they owe their nourishment. It
is therefore impossible to draw from this difference any _static_
definition such as would automatically settle in any particular case the
question whether we are dealing with a plant or an animal. But the
difference may provide the beginning of a _dynamic_ definition of the
two kingdoms, in that it marks the two diver