Thus it will be seen that not only does the life-wave in passing through
one chain of globes dip down into matter and rise out of it again, but the
chain itself in its successive incarnations does exactly the same thing.

There are ten schemes of evolution at present existing in our solar system,
but only seven of them are at the stage where they have planets in the
physical world. These are: (1) that of an unrecognized planet Vulcan, very
near the sun, about which we have very little definite information. It was
seen by the astronomer Herschel, but is now said to have disappeared. We at
first understood that it was in its third incarnation; but it is now
regarded as possible that it has recently passed from its fifth to its
sixth chain, which would account for its alleged disappearance; (2) that of
Venus, which is in its fifth incarnation, and also therefore, has only one
visible globe; (3) that of the Earth, Mars and Mercury, which has three
visible planets because it is in its fourth incarnation; (4) that of
Jupiter, (5) that of Saturn, (6) that of Uranus, all in their third
incarnations; and (7) that of Neptune and the two unnamed planets beyond
its orbit, which is in its fourth incarnation, and therefore has three
physical planets as we have.

In each incarnation of a chain (commonly called a chain-period) the wave of
divine Life moves seven times round the chain of seven planets, and each
such movement is spoken of as a round. The time that the life-wave stays
upon each planet is known as a world-period, and in the course of a
world-period there are seven great root-races. As has been previously
explained, these are subdivided into sub-races, and those again into
branch-races. For convenience of reference we may state this in tabular
form: