eas can be considered only as stragglers, attracted to our
shores during uncommonly warm seasons by an abundant supply of food, or
carried by the Gulf stream, or driven by storms to high latitudes.

Some of the smaller reptiles lay their eggs on aquatic plants; and these
must often be borne rapidly by rivers, and conveyed to distant regions
in a manner similar to the dispersion of seeds before adverted to. But
that the larger ophidians may be themselves transported across the seas,
is evident from the following most interesting account of the arrival of
one at the island of St. Vincent. It is worthy of being recorded, says
Mr. Guilding, "that a noble specimen of the _Boa constrictor_ was lately
conveyed to us by the currents, twisted round the trunk of a large sound
cedar tree, which had probably been washed out of the bank by the floods
of some great South American river, while its huge folds hung on the
branches, as it waited for its prey. The monster was fortunately
destroyed after killing a few sheep, and his skeleton now hangs before
me in my study, putting me in mind how much reason I might have had to
fear in my future rambles through the forests of St. Vincent, had this
formidable reptile been a pregnant female, and escaped to a safe
retreat."[908]

CHAPTER XXXIX.

LAWS WHICH REGULATE THE GEOGRAPHICAL DISTRIBUTION OF
SPECIES--_continued_.

Geographical distribution and migration of Fish--of Testaoea--of
Zoophytes--Distribution of Insects--Migratory instincts of some
species--Certain types characterize particular countries--Their
means of dissemination--Geographical distribution and diffusion of
man--Speculations as to the birth-place of the human
species--Progress of human population--Drifting of canoes to vast
distances--On the involuntary influence of man in extending the
range of many other species.

_Geographical Distribution and Migrations of Fish._

Although we are less acquainted with the habitations of marine animals
than with the grouping of the terrestrial species before described, yet
it is well ascertained that their distribution is governed by the same
general laws. The testimony borne by MM. Paron and Lesueur to this
important fact is remarkably strong. These eminent naturalists, after
collecting and describing many thousand species of marine animals which
they brought to Europe from the southern hemisphere, insist most
emphatically on their distin