Criticisms of Theory of Natural Selection. 373 
portance does not admit of being so much as surmised, 
even where the organ has already attained the size and 
degree of elaboration which it presents in the skate. 
In view of all these considerations taken together, 
I freely confess that the difficulty presented by this 
case appears to me of a magnitude and importance 
altogether unequalled by that of any other single case 
—or any series of cases—which has hitherto been en- 
countered by the theory of natural selection. So that, 
if there were many other cases of the like kind to be 
met with in nature, I should myself at once allow that 
the theory of natural selection would have to be dis- 
carded. But inasmuch as this particular case stands 
so far entirely by itself, and therefore out of analogy 
with thousands, or even millions, of other cases 
throughout the whole range of organic nature, I am 
constrained to feel it more probable that the electric 
organ of the skate will some day admit of being mar- 
shalled under the general law of natural selection—in 
just the same way as proved to be the case with the 
conspicuous colouring of those caterpillars, which, as 
explained in the last chapter, at one time seemed to 
constitute a serious difficulty to the theory, and yet, 
through a better knowledge of all the relations in- 
volved, has now come to constitute one of the strongest 
witnesses in its favour. 
I have now stated all the objections of any import- 
ance which have hitherto been brought against the 
theory of natural selection, excepting three, which I 
left to be dealt with together because they form a 
logically connected group. With a brief consideration 
of these, therefore, I will bring this chapter to a close. 
