IMMUTABILITY OF SPECIES. 75 



Moreover, animals of different types, living in the same 

 element, have no sort of similarity as to size. The aquatic 

 Insects, the aquatic Mollusks, fall in with the average size 

 of their class, as well as the aquatic Reptiles and the 

 aquatic Birds, or the aquatic Mammalia ; but there is no 

 common average for either terrestrial or aquatic animals 

 of different classes taken together. And in this lies the 

 evidence that organized beings are independent of the 

 mediums in which they live, as for as their origin is con- 

 cerned, though it is plain that, when created, they were 

 made to suit the element in which they were placed. 



To me these facts show that the phenomena of life are 

 manifested in the physical world, and not through or by 

 it ; that organized beings are made to conquer and assi- 

 milate to themselves the materials of the inorganic world ; 

 that they maintain their original characteristics, notwith- 

 standing the unceasing action of physical agents upon 

 them. And I confess I cannot comprehend how beings so 

 entirely independent of these influences could be produced 

 by them. 



SECTION XV. 



PERMANENCY OF SPECIFIC PECULIARITIES IN ALL ORGANIZED 



BEINGS. 



It was a great step in the progress of science when it 

 was ascertained that species have fixed characters, and 

 that they do not change in the course of time. But this 

 fact, for which we are indebted to Cuvier, 1 has acquired a 

 still greater importance since it has also been established, 

 that even the most extraordinary changes in the mode of 

 existence, and in the conditions under which animals 



1 CUVIER (G.), Rechcrches sur les Paris, 1821, 5 vols., 4to., fig. vol. i, 

 ossements fossiles, etc., Nouv. edit.; sur 1'Ibis, p. cxli. 



