372 HISTORICAL PALAZSONTOLOGY. 
Foraminifera, the Lingule, the Mautili, &c.; and they indicate 
that under given conditions, at present unknown to us, it is 
possible for a life-form to subsist for an almost indefinite period 
without any important modification of its structure. In the 
second place, whilst the facts above mentioned point to some 
general law of progression of the great zoological groups, it 
cannot be asserted that the primeval types. of any given group 
are necessarily “ lower,’ zooiogically speaking, than their 
modern representatives. Nor does this seem to be at all 
necessary for the establishment of the law in question. It 
cannot be asserted, for example, that the Ganoid and Placoid 
Fishes of the Upper Silurian are in themselves less highly 
organised than their existing representatives ; nor can it even 
be asserted that the Ganoid and Placoid orders are low groups 
of the class Pisces. 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 zecessarily or invariably 
more “degraded” or “embryonic” in their structure than 
their more modern representatives. 
It remains to consider very briefly how far Paleontology 
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 Paleontology 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 
Paleontology 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. Upon no other theory can we comprehend how 
the fauna of any given formation is more closely related to 
that of the formation next below in the series, and to that of 
