ISO THE METHOD OF DARWIN. 



etc., that they could not possibly have been 

 derived from a single primitive electric organ. 

 In this respect the difficulty was exactly similar 

 to that of the climbing power in plants. After 

 pointing out that the electric organs of the 

 different electric fishes are not homologous, 

 that they occupy different parts of the body, 

 are differently innervated, etc., Darwin said 

 that the problem which remains is "by what 

 graduated steps these organs have been devel- 

 oped in each separate group of fishes. " In the 

 case of climbing plants he had been able to 

 show many gradations of structure and function, 

 that even when not fully developed the power 

 to climb was serviceable to plants. He said, 

 " The electric organs of fishes offer another case 

 of special difficulty; for it is impossible to con- 

 ceive by what steps these wondrous organs have 

 been produced. But this is not surprising, for 

 we do not even know of what use they are." l 



Darwin mentioned, however, as factors for 

 the solution of the problem, the great differ- 

 ences in the strength of the shocks, the close 

 analogy, as he called it, between the electric 

 organs and muscular tissue, the electrical phe- 

 nomena of ordinary muscle; and called atten- 

 tion to our ignorance of the habits and structure 



1 Origin of Species, pp. 150, 151. 



