discriminative death which the theory of Natural Selection
presupposes.
We cannot doubt for one moment that in certain cases
the increase of animals and plants is sometimes enormous.
This phenomenon is most obvious in connection with
animals or plants which have immigrated into a country
where the conditions are favourable to their well-being.
The wild bees which now exist in millions in New Zealand
are the offspring of two or three hives, which were once
kept in the rooms of Cotton, of Christ Church, Oxford,
and were taken over by him when he went to New Zea
land with Bishop Selwyn. Some years ago fifty sparrows
were sent to the same colony in the hope that they would
increase and multiply and keep in check the insects which
were so troublesome to the agriculturist. They have in
creased to an enormous extent, but they have changed
their food ; and the farmer has found in them foes even
more terrible than blight or caterpillar. The sweet-briar,
taken by a missionary to his Australian home, has flourished
in a surprising manner, turning a cleared farm into an
impenetrable thicket, and has to be torn out with cart-
ropes and teams of horses. A Scotch emigrant took with
him to Australia a thistle in a flower-pot. It was carefully
transferred to the soil, and its growth was affectionately
watched by the exiles from Caledonia. But soon the land
was covered with monstrous thistles, which defied attempts
at extermination.
“ Columbus, in his second voyage, left a few black cattle at
St. Domingo, and these ran wild and increased so much, that
twenty-seven years afterwards herds of from 4000 to 8000 head
were not uncommon. Cattle were afterwards taken from this island
to Mexico, and to other parts of America, and in 1587, sixty-five
years after the conquest of Mexico, the Spaniards exported 64,350
hides from that country and 35,444 from St. Domingo.
In the pampas of Buenos Ayres there were, at the end of the last
century, about twelve million cows and three million horses, besides