ief points. Eggs or very young
animals seem generally to suffer most, but this is not invariably the
case. With plants there is a vast destruction of seeds, but, from some
observations which I have made, I believe that it is the seedlings which
suffer most from germinating in ground already thickly stocked with
other plants. Seedlings, also, are destroyed in vast numbers by various
enemies; for instance, on a piece of ground three feet long and two
wide, dug and cleared, and where there could be no choking from other
plants, I marked all the seedlings of our native weeds as they came up,
and out of the 357 no less than 295 were destroyed, chiefly by slugs
and insects. If turf which has long been mown, and the case would be the
same with turf closely browsed by quadrupeds, be let to grow, the more
vigorous plants gradually kill the less vigorous, though fully grown,
plants: thus out of twenty species growing on a little plot of turf
(three feet by four) nine species perished from the other species being
allowed to grow up freely.

The amount of food for each species of course gives the extreme limit
to which each can increase; but very frequently it is not the obtaining
food, but the serving as prey to other animals, which determines the
average numbers of a species. Thus, there seems to be little doubt that
the stock of partridges, grouse, and hares on any large estate depends
chiefly on the destruction of vermin. If not one head of game were shot
during the next twenty years in England, and, at the same time, if no
vermin were destroyed, there would, in all probability, be less game
than at present, although hundreds of thousands of game animals are now
annually killed. On the other hand, in some cases, as with the elephant
and rhinoceros, none are destroyed by beasts of prey: even the tiger in
India most rarely dares to attack a young elephant protected by its dam.

Climate plays an important part in determining the average numbers of a
species, and periodical seasons of extreme cold or drought, I believe
to be the most effective of all checks. I estimated that the winter of
1854-55 destroyed four-fifths of the birds in my own grounds; and this
is a tremendous destruction, when we remember that ten per cent. is an
extraordinarily severe mortality from epidemics with man. The action of
climate seems at first sight to be quite independent of the struggle for
existence; but in so far as climate chiefly acts in reducing f