Development of Animal Organization. 217 
indecd 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 tie 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 in 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 Maillet, 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. Cuvier*, 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 are found 
in the most ancient strata; reptiles form the predominant Verte- 
brata in the Jura and Chalk formations ; and remains of mam- 
miferous land-quadrupeds 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, Goppert, 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 periods of ancient vegetation, the first ending 
with the Carboniferous formation+. This elder flora of our 
planet was chiefly formed by ferns and tree ferns. Those plants, 
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 sur les Révolutions, &c. See ‘ Recherches sur les Ossemens 
Fossiles,’ 3° éd. 4to, Paris, 1825, i. pp. 54, 146-172. 
+ Histoire des Végétaux fossiles. Paris, 1828-1837, 4to. Compare also 
an abstract of his researches in ‘ Ann. des Sc. Nat.’ tome xv. 1828, pp. 225- 
258. 
