an to any other continent, those composite denizens
which bear evidence of the greatest antiquity have their affinities for the
most part in South America, while the colonists of a more recent character
are South African." ... "Commidendron and Melanodendron are among the woody
Asteroid forms exemplified in the Andine Diplostephium, and in the
Australian Olearia. Petrobium is one of three genera, remains of a group
probably of great antiquity, of which the two others are Podanthus in Chile
and Astemma in the Andes. The Pisiadia is an endemic species of a genus
otherwise Mascarene or of Eastern Africa, presenting a geographical
connection analogous to that of the St. Helena Melhaniae,[72] with the
Mascarene Trochetia."

Whenever such remote and singular cases of geographical affinity as the
above are pointed out, the first {308} impression is to imagine some mode
by which a communication between the distant countries implicated might be
effected; and this way of viewing the problem is almost universally
adopted, even by naturalists. But if the principles laid down in this work
and in my _Geographical Distribution of Animals_ are sound, such a course
is very unphilosophical. For, on the theory of evolution, nothing can be
more certain than that groups now broken up and detached were once
continuous, and that fragmentary groups and isolated forms are but the
relics of once widespread types, which have been preserved in a few
localities where the physical conditions were especially favourable, or
where organic competition was less severe. The true explanation of all such
remote geographical affinities is, that they date back to a time when the
ancestral group of which they are the common descendants had a wider or a
different distribution; and they no more imply any closer connection
between the distant countries the allied forms now inhabit, than does the
existence of living Equidae in South Africa and extinct Equidae in the
Pliocene deposits of the Pampas, imply a continent bridging the South
Atlantic to allow of their easy communication.

_Concluding Remarks on St. Helena._--The sketch we have now given of the
chief members of the indigenous fauna and flora of St. Helena shows, that
by means of the knowledge we have obtained of past changes in the physical
history of the earth, and of the various modes by which organisms are
conveyed across the ocean, all the more important facts become readily
intelligible. We have here