" Hence it is quite credible that the presence of a feline
animal in large numbers in a district might determine, through the
intervention first of mice and then of bees, the frequency of certain
flowers in that district!
In the case of every species, many different checks, acting at
different periods of life, and during different seasons or years,
probably come into play; some one check or some few being generally
the most potent, but all concurring in determining the average number
or even the existence of the species. In some cases it can be shown
that widely-different checks act on the same species in different
districts. When we look at the plants and bushes clothing an entangled
bank, we are tempted to attribute their proportional numbers and kinds
to what we call chance. But how false a view is this! Every one has
heard that when an American forest is cut down, a very different
vegetation springs up; but it has been observed that the trees now
growing on the ancient Indian mounds, in the Southern United States,
display the same beautiful diversity and proportion of kinds as in the
surrounding virgin forests. What a struggle between the several kinds
of trees must here have gone on during long centuries, each annually
scattering its seeds by the thousand; what war between insect and
insect--between insects, snails, and other animals with birds and
beasts of prey--all striving to increase, and all feeding on each
other or on the trees or their seeds and seedlings, or on the other
plants which first clothed the ground and thus checked the growth of
the trees! Throw up a handful of feathers, and all must fall to the
ground according to definite laws; but how simple is this problem
compared to the action and reaction of the innumerable plants and
animals which have determined, in the course of centuries, the
proportional numbers and kinds of trees now growing on the old Indian
ruins!
The dependency of one organic being on another, as of a parasite on
its prey, lies generally between beings remote in the scale of nature.
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