his lecture, Sir Joseph wrote that in ascending the
mountains in Madeira there is but little replacement of lowland species
by those of a higher northern latitude. "Plants become fewer and fewer
as we ascend, and their places are not taken by boreal ones, or by but
very few."): the depth is so great; there is nothing geologically in
the islands favouring the belief; there are no endemic mammals or
batrachians. Did not Bunbury show that some Orders of plants were
singularly deficient? But I rely chiefly on the large amount of specific
distinction in the insects and land-shells of P. Santo and Madeira:
surely Canary and Madeira could not have been connected, if Madeira and
P. Santo had long been distinct. If you admit Atlantis, I think you are
bound to admit or explain the difficulties.

With respect to cold temperate plants in Madeira, I, of course, know
not enough to form an opinion; but, admitting Atlantis, I can see their
rarity is a great difficulty; otherwise, seeing that the latitude
is only a little north of the Persian Gulf, and seeing the long
sea-transport for seeds, the rarity of northern plants does not seem to
me difficult. The immigration may have been from a southerly direction,
and it seems that some few African as well as coldish plants are common
to the mountains to the south.

Believing in occasional transport, I cannot feel so much surprise at
there being a good deal in common to Madeira and Canary, these being
the nearest points of land to each other. It is quite new and very
interesting to me what you say about the endemic plants being in so
large a proportion rare species. From the greater size of the workshop
(i.e., greater competition and greater number of individuals, etc.)
I should expect that continental forms, as they are occasionally
introduced, would always tend to beat the insular forms; and, as in
every area, there will always be many forms more or less rare tending
towards extinction, I should certainly have expected that in islands
a large proportion of the rarer forms would have been insular in their
origin. The longer the time any form has existed in an island into which
continental forms are occasionally introduced, by so much the chances
will be in favour of its being peculiar or abnormal in nature, and at
the same time scanty in numbers. The duration of its existence will
also have formerly given it the best chance, when it was not so rare, of
being widely distributed to adjoinin