224 OEaANS OP EXTilBMB PEKFECTIOK. [Chap. VL 



have been formed by natural selection, seems, I freely 

 confess, absurd in the highest degree. When it was first 

 said that the sun stood still and the world turned round, 

 the common sense of mankind declared the doctrine 

 false; but the old saying of Vox populi, vox Dei, aa 

 every philosopher knows, cannot be trusted in science. 

 Eeason tells me, that if numerous gradations from a 

 simple and imperfect eye to one complex and perfect 

 can be shown to exist, each grade being useful to its 

 possessor, as is certainly the case; if further, the eye 

 ever varies and the variations be inherited, as is like- 

 wise certainly the case; and if such variations should 

 be useful to any animal under changing conditions of 

 life, then the difficulty of believing that a perfect and 

 complex eye could be formed by natural selection, 

 though insuperable by our imagination, should not 

 be considered as subversive of the theory.. How a nerve 

 comes to be sensitive to light, hardly concerns us more 

 than how life itself originated; but I may remark that, 

 as some of the lowest organisms, in which nerves can- 

 not be detected, are capable of perceiving light, it does 

 not seem impossible that certain sensitive elements 

 in their sarcode should become aggregated and de- 

 veloped into nerves, endowed with this special sensi- 

 bility. 



In searching for the gradations through which an 

 organ in any species has been perfected, we ought to 

 look exclusively to its lineal progenitors; but this is 

 scarcely ever possible, and we are forced to look to 

 other species and genera of the same group, that is to 

 the collateral descendants from the same parent-form, 

 in order to see what gradations are possible, and for the 

 chance of some gradations having been transmitted in 



