3o8 LAMARCK, HIS LIFE AND WORK 



power of sight ; also it possesses only vestiges of the 

 organ of which it is the seat ; and yet these vestiges 

 are wholly concealed under the skin and other parts 

 which cover them, and do not permit the least access 

 to the light. 



" The Proteus, an aquatic reptile allied to the sala- 

 mander in its structure, and which lives in the dark 

 subterranean waters of deep caves, has, like the As- 

 palax, only vestiges of the organs of sight — vestiges 

 which are covered and concealed in the same manner. 



" We turn to a decisive consideration relative to 

 this question. 



" Light does not penetrate everywhere ; conse- 

 quently animals which habitually live in situations 

 where it does not penetrate lack the occasion of 

 exercising the organs of sight, if nature has provided 

 them with them. Moreover, the animals which make 

 part of the plan of organization in which eyes are 

 necessarily present, have originally had them. How- 

 ever, since we find them among those which are de- 

 prived of the use of this organ, and which have only 

 vestiges concealed and covered over, it should be 

 evident that the impoverishment and even the dis- 

 appearance of these organs are the result of a con- 

 stant lack of exercise. 



" What proves it is that the organ of hearing is 

 never in this condition, and that we always find it in 

 the animals when the nature of their organization 

 should require its existence ; the reason is as follows. 



" The cause of sound, that which, moved by the 

 shock or the vibrations of bodies, transmits to the 

 organ of hearing the impression which it receives, 

 penetrates everywhere, traverses all the media, and 

 even the mass of the densest bodies : from this it re- 

 sults that every animal which makes a part of a plan 

 of organization to which hearing is essential, has 

 always occasion to exercise this organ in whatever 

 situation it lives. So, among the vertebrate animals 



