Development of Animal Organization, 217 



indeed among these recent forms cannot be explained without 

 the aid of various suppositions ; and, on the other hand, there is 

 a great number of superfluous species in the existence of so 

 many fossil forms. An unprejudiced inquiry shows evidently 

 that some tribes or families of plants and animals were predo- 

 minant in one, others in another period, and that a small num- 

 ber of groups, on the contrary, have been in existence in all the 

 different periods, that they always have had their representatives 

 in some species, and are not wanting iu the recent order of 

 nature. 



There still remains, before we conclude our remarks on the 

 history of organic bodies on the surface of our earth, one ques- 

 tion which deserves discussion. Is it possible to deduce any 

 general conclusions concerning the successive development of 

 the organic world from the investigation of fossil remains, and 

 by comparing them with each other? This question ought not 

 to be misapprehended. We can reject indeed the hypothesis 

 of De Maillct, who admitted that a bird was the offspring of 

 a flying-fish, and yet believe that geology supplies us with 

 proofs of a successive development, of an advance in the com- 

 plication of organic beings. Cuvicr*, for instance, admitted 

 such a succession, although he was far from admitting such 

 genealogies. He stated that reptiles are found considerably 

 earlier, or in more ancient strata, than mammals, and that the 

 more recent formations contain species which appoach nearest 

 to those now living. Remains of Mollusca and fishes arc found 

 in the most ancient strata; reptiles form the predominant Vertc- 

 brata in the Jura and Chalk formations; and remains of mam- 

 miferous land-cjuadrupcds are, according to his view, only to be 

 found in Tertiary strata. Similar remarks have been made by 

 those writers who have devoted themselves to the investigation 

 of fossil plants — Adolphe Brongniart, Gcippert, and others: 

 they admit that the earliest vegetation was very simple, and that 

 there was a slow advance and manifest progress in succeeding 

 periods towards the now living vegetable kingdom. Brongniart 

 admits four great ])eriods of ancient vegetation, the first ending 

 with the Carboniferous formation f. This elder flora of our 

 planet was chiefly formed by ferns and tree ferns. Those i)lants, 

 which now constitute only one-fortieth of all the known living 

 species, prevailed then in such a remarkable manner that they 

 formed two-thirds of all the species which made up the flora of 



• Discours 8ur les R<^volutions, &c. Sec ' Recherches sur Ics Ossemens 

 Fossiles,' :J* ed. 4to, Paris, 1825, i. pp. 54, 146-17l^ 



t Ilistoire des Vcgetaux fossiles. Paris, 18"28-1837, 4to. Compare also 

 an abstract of his researches in ' Ann. des So. Nat.' tome xv. 1828, pp. 225- 

 258. 



