and that therefore the natural sequence of the species by affinity is also
- In countries of a similar climate, but separated by a wide sea or lofty mountains, the families, genera and species of the one are often represented by closely allied families, genera and species peculiar to the other.
Geology.
- The distribution of the organic world in time is very similar to its present distribution in space.
- Most of the larger and some small groups extend through several geological periods.
- In each period, however, there are peculiar groups, found nowhere else, and extending through one or several formations.
- Species of one genus, or genera of one family occurring in the same geological time are more closely allied than those separated in time.
- As generally in geography no species or genus occurs in two very distant localities without being also found in intermediate places, so in geology the life of a species or genus has not been interrupted. In other words, no group or species has come into existence twice.
- The following law may be deduced from these facts:—Every species has come into existence coincident both in space and time with a pre-existing closely allied species.
This law agrees with, explains and illustrates all the facts connected with the following branches of the subject:—1st. The system of natural