Development of Animal Organization^ 215 



microscopic species, some Infusoria and Algje, which belong to 

 the present creation are found likewise in very old strata, as in 

 those of the Carboniferous or even of the Silurian group*. 

 There are two suppositions we can make respecting the manner 

 of the extinction of species in the history of the earth. We can 

 ascribe that extinction to a change of external conditions, by 

 the influence of which the life of the organisms was affected, and 

 by whose continued action the species, formed for other condi- 

 tions, diminished in number, and sooner or later perished alto- 

 gether ; or we can ascribe the fact to the sudden action of some 

 ▼iolent revolutions on the globe, by which plants and animals 

 were destroyed. The latter explanation formerly predominated; 

 the assumption of a general cataclysm, by which the inhabited 

 earth was destroyed, led easily and almost unavoidably to this 

 belief. The more extended knowledge of facts showed after- 

 wards that a deluge recorded in human history could not explain 

 the great diversity of fossil remains which were found in the 

 strata of mountains ; and the hypothesis was modified by the 

 assumption of several geological cataclysms, by which, during 

 the modelling and remodelling of the earth, various generations 

 of plants and animals perished, and were imbedded in the de- 

 posits of the water f. In our time the explanation is generally 

 given up ; but it seems that some writers go too far by an entire 

 denial of lesser or much more sudden revolutions, which were 

 natural consequences of the upheaving of volcanos and of chains 

 of plutonic mountains. 



That there was a succession of new species of plants and ani- 

 mals, a repetition of distinct creations, is, as I have already said, 

 a conception which seems not so favourable to acceptance. 

 There is nothing, indeed, in actual observation of the present 

 order of nature that can be compared to this new creation. 

 Almost daily, it is true, some formerly unknown species of 

 plants or animals is registered in our catalogues ; but there is 

 no more reason to think that they are really new than to believe 

 that the New World was upheaved from the ocean at a later 

 period than Europe because its discovery was only made in the 

 15th century. There is, however, a power of evidence which 

 cannot be annihilated by our doubts or by the difficulty of un- 

 derstanding the facts ; and, in our researches on natural objects 

 and phenomena, it is not fair to ask what we can explain before 

 we see what we are obliged to admit by the authority of obser- 



♦ Microeeologie. Das Erden- und Felsen-schaffende Wirken, &c. Leip- 

 xig, 1854, fol. S. xiv. 



t Cuvier, for instance, 8]>eaks often of such " catastrophes et revolu- 

 tions subites," in his famous and always remarkable ' Discours sur les 

 Revolutions de la Surface du Globe.' 



