37 2 Darwin, and after Darwin. 



lation in favour of natural selection, and therefore if 

 for the sake of saving an hypothesis we assume that 

 the organ as it now stands must be of some use to the 

 existing skate, we should still have to face the question 

 Of what conceivable use can those initial stages of its 

 formation have been, when first the muscle-elements 

 began to be changed into the very different electrical- 

 elements, and when therefore they became useless as 

 muscles while not yet capable of performing even so 

 much of the electrical function as they now perform ? 

 Lastly, we must remember that not only have we 

 here the most highly specialized, the most complex, 

 and altogether the most elaboratively adaptive organ 

 in the animal kingdom ; but also that in the formation 

 of this structure there has been needed an altogether 

 unparalleled expenditure of the most physiologically 

 expensive of all materials- namely, nervous tissue. 

 Whether estimated by volume or by weight, the 

 quantity of nervous tissue which is consumed in the 

 electric organ of the skate is in excess of all the rest 

 of the nervous system put together. It is need- 

 less to say that nowhere else in the animal king- 

 dom except, of course, in other electric fishes is 

 there any approach to so enormous a development of 

 nervous tissue for the discharge of a special function. 

 Therefore, as nervous tissue is, physiologically speak- 

 ing, the most valuable of all materials, we are forced 

 to conclude that natural selection ought strongly to 

 have opposed the evolution of such organs, unless from 

 the first moment of their inception, and throughout the 

 whole course of their development, they were of some 

 such paramount importance as biologically to justify so 

 unexampled an expenditure. Yet this paramount im- 



