UNVERIFIED DEDUCTIONS. 1 79 



because of the inaccessibility of the facts. He 

 had the satisfaction of living to see the whole 

 biological world applying itself to the work of 

 bringing out the consequences of his theories. 

 It is not a part of the present purpose, even if it 

 were possible, to follow out the logical history 

 of the subsequent work based on those theo- 

 ries. But it will be of interest to notice a few 

 instances in which he made deductions which 

 he could not verify. Some of these have been 

 since verified by others, and some still remain 

 unverified. They vary all the way from confi- 

 dent predictions to vague expressions of a wish 

 that some one would make observations that he 

 thought would bear fruit. 



There is one instance of a difficulty in the 

 way of Darwin's theories which is of especial 

 importance. He outlined a possible explana- 

 tion, but the difficulty has proved itself so stub- 

 born that even some of his adherents feel that 

 his theories could not face many of the same 

 kind. The problem is almost exactly similar 

 to that of climbing plants, and its interest is 

 increased by some recent work that has been 

 done towards its solution. 



Electric organs occur in various unrelated 

 species of fishes, and differ so widely in their 

 position in the body, their mode of innervation, 



