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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



lastly, the more highly developed angiosperms, hoth monocotyledonous 

 and dicotyledonous, do not become abundant until the tertiary period. 

 It is a remarkable fact, as he justly observes, that the exogens, which 

 comprise four-fifths of living plants, — a division to which all our na- 

 tive European trees, except the Coniferse, belong, and which embraces 

 all the Composite, Leguminosse, Umbelliferse, Cruciferse, Heaths, and 

 so many other families, — are wholly unrepresented by any fossils 

 hitherto discovered in the primary and secondary formations from the 

 Silurian to the oolitic inclusive. It is not till we arrive at the cre- 

 taceous period that they begin to appear, sparingly at first, and only 

 playing a conspicuous part together with the palms and other en- 

 dogens in the tertiary epoch. 



To these writers, for whose judgement I have the greatest respect, 

 I might add the testimony of other high authorities in support of 

 similar views, but I shall content myself by concluding with a refer- 

 ence to Professor Bronn of Heidelberg, with whose £ Index Palseonto- 

 logicus,' lately published, every geologist is, I trust, acquainted. 

 From the ample data supplied by 24,000 species of fossil animals 

 and plants enumerated in this elaborate catalogue, the author deduces 

 not only the law of an increasing number and variety of species in the 

 more modern, as compared to the more ancient formations, but also 

 the successive introduction of the higher and more perfectly or- 

 ganized classes. I must not, however, lead you to suppose that 

 every name of weight is ranged on one side of this controverted 

 question, for in the communications made during the last year to the 

 Academy of Sciences in Paris, I find a declaration by M. Constant 

 Prevost, that he is not satisfied with the palseontological evidence in 

 support of the doctrine of successive development, and a no less de- 

 cided and more circumstantial statement by M. Alcide D'Orbigny of 

 his reasons for dissenting from the same theory*. 



Before I go into details, whether of fact or argument, on this 

 question, I shall proceed, for the sake of enabling you the more 

 readily to follow my train of reasoning, to make a brief preliminary 

 statement of the principal points which I expect to establish in oppo- 

 sition to the theory of successive development. 



* C. Prevost, Comptes Rendus, Sept. 1850, vol. xxxi. p. 461 ; and A. D'Orbigny, 

 Ibid. June 1850, vol. xxx. p. 807. 



