THE MADEIRA BEETLES-CONCLUSION. 379 



"Light cannot penetrate everywhere, and as a 

 consequence, animals which live habitually in places 

 which it cannot reach, do not have an opportunity of 

 using eyes, even though they have got them ; but 

 animals which form part of a system of organization 

 which comprises eyes as an invariable rule among its 

 organs, must have had eyes originally. Since then we find 

 among these animals some which have lost their eyes, 

 and which have only concealed traces of these organs, 

 it is evident that the impoverishment, and even disap- 

 pearance of the organs in question, must be the effect 

 of long-continued disuse. 



" A proof of this is to be found in the fact that the 

 organ of hearing is never in like case with that of sight; 

 we always find it in animals of whose system of organi- 

 zation hearing is a component part ; and for the follow- 

 ing reason, namely, that sound, which is the effect of 

 vibration upon the ear, can penetrate everywhere, and 

 pass even through massive intermediate bodies. Any 

 animal, therefore, with an organic system of which the 

 ear is an essential part, can always find a use for its 

 ears, no matter where it inhabits. We never, therefore, 

 come upon rudimentary ears among the vertebrata, 

 and when, going down the scale of life lower than the 

 vertebrata, we come to a point at which the ear is no 

 longer to be found ; we never come upon ears again 

 in any lower class. 



" Not so with the organ of sight : we see this organ 

 disappear, reappear, and disappear again with the pos- 

 sibility or impossibility of using eyes on the part of the 

 creature itself.* 



* ' Phil. Zool.,' torn. i. p. 244. 



