We here see in two distant countries a similar relation between plants and insects of the same families, though the species of both are different. When man is the agent in introducing into a country a new species this relation is often broken

We shall best understand the probable course of natural selection by taking the case of a country undergoing some slight physical change, for instance, of climate. The proportional numbers of its inhabitants will almost immediately undergo a change, and some species will probably become extinct.

Mere chance ... alone would never account for so habitual and large an amount of difference as that between varieties of the same species.

It is not that these countries, so rich in species, do not by a strange chance possess the aboriginal stocks of any useful plants, but that the native plants have not been improved by continued selection up to a standard of perfection comparable with that given to the plants in countries anciently civilised.

Species that struggle to adapt to survive will become extinct.

Species of the same genus would occasionally exhibit reversions to lost ancestral characters.