changed
simultaneously throughout the world, it must not be supposed that this
expression relates to the same year, or even to the same century, or
even that it has a very strict geological sense; for if all the marine
animals now living in Europe, and all those that lived in Europe during
the pleistocene period (a very remote period as measured by years,
including the whole glacial epoch) were compared with those now existing
in South America or in Australia, the most skilful naturalist would
hardly be able to say whether the present or the pleistocene inhabitants
of Europe resembled most closely those of the southern hemisphere. So,
again, several highly competent observers maintain that the existing
productions of the United States are more closely related to those which
lived in Europe during certain late tertiary stages, than to the
present inhabitants of Europe; and if this be so, it is evident that
fossiliferous beds now deposited on the shores of North America would
hereafter be liable to be classed with somewhat older European beds.
Nevertheless, looking to a remotely future epoch, there can be little
doubt that all the more modern MARINE formations, namely, the upper
pliocene, the pleistocene and strictly modern beds of Europe, North and
South America, and Australia, from containing fossil remains in some
degree allied, and from not including those forms which are found
only in the older underlying deposits, would be correctly ranked as
simultaneous in a geological sense.

The fact of the forms of life changing simultaneously in the above large
sense, at distant parts of the world, has greatly struck those admirable
observers, MM. de Verneuil and d'Archiac. After referring to the
parallelism of the palaeozoic forms of life in various parts of Europe,
they add, "If struck by this strange sequence, we turn our attention to
North America, and there discover a series of analogous phenomena,
it will appear certain that all these modifications of species, their
extinction, and the introduction of new ones, cannot be owing to mere
changes in marine currents or other causes more or less local and
temporary, but depend on general laws which govern the whole animal
kingdom." M. Barrande has made forcible remarks to precisely the same
effect. It is, indeed, quite futile to look to changes of currents,
climate, or other physical conditions, as the cause of these great
mutations in the forms of life throughout the world,