On the contrary, they are high groups; but then it
must be remembered that these are probably not really the first
Fishes, and that if we meet with Fishes at some future time in
the Lower Silurian or Cambrian, these may easily prove to be
representatives of the lower orders of the class. This question
cannot be further entered into here, as its discussion could be
carried out to an almost unlimited length; but whilst there are
facts pointing both ways, it appears that at present we are not
justified in asserting that the earlier types of each group--so far
as these are known to us, or really are without predecessors--are
_necessarily_ or _invariably_ more "degraded" or "embryonic" in
their structure than their more modern representatives.
It remains to consider very briefly how far Palaeontology supports
the doctrine of "Evolution," as it is called; and this, too, is a
question of almost infinite dimensions, which can but be glanced at
here. Does Palaeontology teach us that the almost innumerable kinds
of animals and plants which we know to have successively flourished
upon the earth in past times were produced separately and wholly
independently of each other, at successive periods? or does it
point to the theory that a large number of these supposed distinct
forms, have been in reality produced by the slow modification of a
comparatively small number of primitive types? Upon the whole, it
must be unhesitatingly replied that the evidence of Palaeontology
is in favour of the view that the succession of life-forms upon
the globe has been to a large extent regulated by some orderly
and constantly-acting law of modification and evolution.
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