und
almost every year in the London Docks. It is therefore probable, that when
species of this family have a very wide range they have been assisted in
their migrations by man, though their habit of clinging to trees also
renders them likely to be floated with large pieces of timber to
considerable distances. Dr. Percival Wright, to whom I am indebted for much
information on the productions of the Seychelles Archipelago, informs me
that the last-named species varies greatly in colour in the different
islands, so that he could always tell from which particular island a
specimen had been brought. This is analogous to the curious fact of certain
lizards on the small islands in the Mediterranean being always very
different in colour from those of the mainland, usually becoming rich blue
or black (see _Nature_, Vol. XIX. p. 97); and we thus learn how readily in
some cases differences of colour are brought about, either directly or
indirectly, by local conditions.

Snakes, as is usually the case in small or remote islands, are far less
numerous than lizards, only two species being known. One, _Dromicus
seychellensis_, is a peculiar species of the family Colubridae, the rest of
the genus being found in Madagascar and South America. The other, _Boodon
geometricus_, one of the Lycodontidae, or fanged ground-snakes, is also
peculiar. So far, then, as the reptiles are {432} concerned, there is
nothing but what is easily explicable by what we know of the general means
of distribution of these animals.

We now come to the Amphibia, which are represented in the Seychelles by two
tailless and two serpent-like forms. The frogs are _Rana mascareniensis_,
found also in Mauritius, Bourbon, Angola, and Abyssinia, and probably all
over tropical Africa; and _Megalixalus seychellensis_ a peculiar tree-frog
having allies in Madagascar and tropical Africa. It is found, Dr. Wright
informs me, on the Pandani or screw-pines; and as these form a very
characteristic portion of the vegetation of the Mascarene Islands, all the
species being peculiar and confined each to a single island or small group,
we may perhaps consider it as a relic of the indigenous fauna of that more
extensive land of which the present islands are the remains.

The serpentine Amphibia are represented by two species of Caecilia. These
creatures externally resemble large worms, except that they have a true
head with jaws and rudimentary eyes, while internally they have of cours