6 6 OF THE DISPERSION OF CETACEA.
correct, even with respect to the majority of cetacese, but cpn-»
tends, that it is not applicable, if we can rely upon the present
state of our information, to some of the whales and cachalots
which are capable of traversing the equatorial seas
from one polar region to the other. It is generally admitted,
as he observes, that the best known among the great cetaceae,
are spread through all seas on the globe, and that the.sanae
species o f whales or macrocephalous cachalots belonging to
the northern seas are found in the great ocean, whether in the
waters which wash the north-west coast of America, or in the
seas of Cape Horn, or southward of New Holland. The whale-
fishers whom we have consulted on this subject have, in fact,
always affirmed this identity | and the whales or fishes that
we have seen under all the parallels of the north or south, or
under the equator, in the Pacific, as well as Atlantic Ocean,
have appeared to us to differ in no respect from the species of
cetaceae in the northern seas, such as they have been der
scribed. _But we know that the same remark'does not hold:
with respect to dolphins; these are subject to the laws, imposed
upon all animals in a state of nature; they do not go
beyond certain limits. Within these limits are all the pp^dir
tions appropriated to their support; there they find , the kind
of nourishment which is proper for them, the nature and temperature
of the waters to which their organs are accustomed;
all the requisites of their existence are included under these
latitudes: thus to the south belong the delphinapter of
Perqn, and its representative in the north is the beluga:
thus the dolphins of the coasts of Iceland or even of Eufope,
are by no means the same as those of the antarctic seas.” *
The dispersion of fishes has been still less an object of research,
but in this instance the leading facts direct us to. a
similar conclusion. The fishes of the Red Sea, as Mr. Lyell
has observed, are said to differ entirely from those of the Mediterranean.
Flying, fish are almost confined to the inter-
tropical oceans, and different species are found in the Atlantic
and in the eastern seas. The electric gymnotus belongs exclusively
to America, and the silurus electricus to the rivers of
• Lesson, Hist. Nat, des Cétacés, p. 9.
Africa, while the torpedo, which is dispersed over all the tropical
seas, is found also in the temperate regions.*
The greatest difficulty connected with the distribution of
fiè|iës' is the discovery of the same species in fresh-water
lakes remote from each other, and spread at great distances
and at different elevations over mountainous régions. Such
phenomena have a close relation to those which are displayed,
by the diffusion of aquatic plants of the same species through
inland seas and lakes ; and the only satisfactory solutioi&df
these facts is fo be obtained by reference to inundations and
land-floods, the frequent occurrence pf which in different
periods is, attested-by historical and by geological proofs. It
is supposed by Gmelin and by Mr. Lyell, pitat birds, and" particularly
the anseres, retain occasionally the mintifè eggs ófi
fishes among their feathers, and transport them from one lake’
to another.f ’ i
M. M. Péron and Le^Sueur have adopted a similar conclusion
respecting the lowers departments,Of'marine animals." Thèy-
begin with asserting a ju s t claim’ to attention?:1 ^ 'N '0-v-öyag’ëri
has collected a gifeater number óf animals than we hàvë doriè
in the southern-hemisphere ; we have'^óbSsetved, described,f
and drawn figures of them all in their native spots : wè have
brought w ith e s many thousand species into ' Eu#pply£ where
they are deposited in the Museum of Natural History at Paris.
Let these numerous animals oèî compared with thoSe b f our
hemisphere, and the problem of their iÜentity or diversity
will be solved, not only-with regard to speci,e§‘,of a more perfect
organization, but even with respect to all! th'oëè’which
are of more simple structure, and which, ©n that account,'
might seem likely to have received from nature less-'5variety
of. form. Let those who doubt, examine b ó t’ merely <th^spC-
cies of Doris, of Aplysia, of Salpa, of ,Nérèis, Aphiiîome,
Amphitrite, and that multitude of molluécée and worms,
which offered themselves successively to our observation ; let
them descend also to the Holothuriæ, to the Actiniæ, the Heroes,
the Medusee; let them extend their researches even to
those shapeless sponges, which all agree in regarding as the?
* LyellV Principles of Geology, p. 2f.
•j* Gmelin in Amænitat. Acad. f5,--Lye ll’s Geology, yol iii.' £. 3. Ill 2 ■