538 ZOOLOGY. 



whose organization is not calculated so as to preserve them 

 from the injurious effects of such an evaporation, can live 

 only in water, and perish promptly in the air. Now the 

 animal economy can only meet this exigency by means of a 

 great complication in its structure. In fact, if the respira- 

 tion must be active, it becomes necessary that the respiratory 

 surface be then lodged profoundly in some internal cavity 

 where the air can only be renewed in the quantities necessary 

 for the support of life. To secure this renewal, it is essential 

 that the respiratory apparatus be complicated with motor 

 organs proper to secure it ; to prevent the desiccation of any 

 portion of the surface of the body, it becomes necessary also 

 that the distribution of the liquids in the various parts of the 

 body be accomplished easily, and that there exist an active 

 circulation, or otherwise that this surface be clothed with a 

 tunic scarcely permeable. This is so true, that even in fishes, 

 in which the circulation is so complete, but takes place 

 slowly, and in which the capillary network is not very close, 

 death takes place rapidly, as a necessary consequence of 

 the desiccation of a part of the body of the posterior por- 

 tion, for example even when this portion alone is exposed 

 to the air, all the rest of the animal remaining plunged under 

 water. 



We might also add, that in water, alimentation is possible 

 with instruments of prehension and of motion less perfect 

 than in air, in which the transport of foreign matters re- 

 quired by the animal is more difficult to accomplish. Thus, 

 under all its more essential relations, life is, in some measure, 

 easier to sustain in the bosom of the waters than on the sur- 

 face of the dry land ; it necessitates in the atmosphere phy- 

 siological instruments more complex and more perfect; 

 therefore the waters are the natural element of the animals 

 placed lower in the scale of the zoological series ; and if the 

 productions of the creation have succeeded each other in the 

 same order of the transitory conditions through which each 

 animal passes during the period of its development, we may- 

 conclude that it was in the middle of the waters that ani- 

 mated beings appeared first, a result which accords with the 

 observations of geologists and the assertions of Scripture. The 

 physiologist may in this manner give an account of the actual 

 mode of distribution of animals between the two geological 

 elements which divide the surface of the globe, land and 

 water: but these fundamental differences are not the only 



