472 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 mst 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- 
