It has, however, been observed that, though no European dogs thrive well in India, the Newfoundland dog, originating from a severe climate, can hardly be kept alive.

A better case, perhaps, is furnished by merino sheep, which, when imported directly from England, do not thrive, while those which have been bred in the intermediate climate of the Cape of Good Hope do much better.

When geese were first introduced into Bogota, they laid few eggs at long intervals, and few of the young survived.

By degrees, however, the fecundity improved, and in about twenty years became equal to what it is in Europe.

According to Garcilaso, when fowls were first introduced into Peru they were not fertile, whereas now they are as much so as in Europe.
Plants furnish much more important evidence.