Professor Pictet on the Succession of Animals. 273 



discovery of a very small number of fragments ; the remains 

 of terrestrial animals are seldom fossilized but by great 

 catastrophes and sudden inundations, which always perform 

 but a trifling part when compared with the slow and normal 

 deposits of tranquil waters. May it not happen that new 

 discoveries will yet bring to light, from the ancient forma- 

 tions, animals of whose existence we have not now any idea ? 

 A second observation is, that if we seek to compare the 

 actual state of the globe with the various ancient creations, 

 we will perceive that the superior degree of perfection of the 

 organism, cannot always furnish very conclusive results as 

 to the perfection of faunas. Thus, without taking into ac- 

 count the presence of man, shall we assert that the fauna of 

 Asia is superior to that of Europe, because its highest grade 

 is the oran-outang ? and shall we place the fauna of New 

 Holland below all others, because its mammifera are almost 

 all didelphous animals 1 Such conclusions, however, would 

 be almost as legitimate as some of those which have been 

 established by the comparison of geological faunas. 



Now that we have explained the principal facts relative 

 to the distribution of fossils in formations, and discussed the 

 laws which have been deduced from them, respecting the 

 succession of organized beings on the surface of the globe, 

 it remains for us to take a glance at the theories which 

 have been proposed to explain this series of different faunas. 

 Leaving the more certain domain of facts, we must, for a 

 short time, enter the less secure field of theoretical con- 

 jecture. 



The investigation of the causes of the succession of orga- 

 nized beings is connected, on the one hand, with cosmogonie 

 theories, and, on the other, with the most delicate principles 

 of animal physiology. The solution of this question, accord- 

 ingly, is of high importance, and may be regarded as the 

 proper object to which the study of palaeontology ought to be 

 directed. But, perhaps, the science is not yet far enough 

 advanced to furnish sufficient grounds to enabfe us to come 

 to a sound conclusion. I shall here explain the principal 

 theories that have been proposed, and point out the objec- 

 tions, of greater or less weight, which may be urged against 



