The competition will generally be most severe, as formerly explained and illustrated by examples, between the forms which are most like each other in all respects.

Hence the improved and modified descendants of a species will generally cause the extermination of the parent-species; and if many new forms have been developed from any one species, the nearest allies of that species, i.

e.

the species of the same genus, will be the most liable to extermination.

Thus, as I believe, a number of new species descended from one species, that is a new genus, comes to supplant an old genus, belonging to the same family.