3/2 HISTORICAL PALEONTOLOGY. 



Foranttiiifera, the Ltngula, the Nautili, &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," zoologically speaking, than their 

 modern representatives. Nor does this seem to be at all 

 necessary for the establishment oC 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 m?y 

 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. 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 



