That climate acts in main part indirectly by favouring other species, we clearly see in the prodigious number of plants which in our gardens can perfectly well endure our climate, but which never become naturalised, for they cannot compete with our native plants nor resist destruction by our native animals.

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

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

A grain in the balance will determine which individual shall live and which shall die - which variety or species shall increase in number, and which shall decrease, or finally become extinct.

On the ordinary view of each species having been independently created, we gain no scientific explanation.

All that at present can be said with certainty, is that, as with the individual, so with the species, the hour of life has run its course, ans is spent.