F. You will grant then, firstly, that all plants and animals increase
very rapidly, and that unless they were in some manner checked, the world
would soon be overstocked. Take cats, for instance; see with what
rapidity they breed on the different runs in this province where there is
little or nothing to check them; or even take the more slowly breeding
sheep, and see how soon 500 ewes become 5000 sheep under favourable
circumstances. Suppose this sort of thing to go on for a hundred million
years or so, and where would be the standing room for all the different
plants and animals that would be now existing, did they not materially
check each other’s increase, or were they not liable in some way to be
checked by other causes? Remember the quail; how plentiful they were
until the cats came with the settlers from Europe. Why were they so
abundant? Simply because they had plenty to eat, and could get
sufficient shelter from the hawks to multiply freely. The cats came, and
tussocks stood the poor little creatures in but poor stead. The cats
increased and multiplied because they had plenty of food and no natural
enemy to check them. Let them wait a year or two, till they have
materially reduced the larks also, as they have long since reduced the
quail, and let them have to depend solely upon occasional dead lambs and
sheep, and they will find a certain rather formidable natural enemy
called Famine rise slowly but inexorably against them and slaughter them
wholesale. The first proposition then to which I demand your assent is
that all plants and animals tend to increase in a high geometrical ratio;
that they all endeavour to get that which is necessary for their own
welfare; that, as unfortunately there are conflicting interests in
Nature, collisions constantly occur between different animals and plants,
whereby the rate of increase of each species is very materially checked.
Do you admit this?