Criticisms of Theory of Natural Selection. 371 
organ, even after it has attained its full development, 
continues its growth with the growth of the fish, and 
this in a much higher ratio, either than the tail alone, 
or the whole animal. Lastly, Prof. Burdon Sanderson 
finds that section for section the organ in the skate is 
as efficient as it is in Torpedo. It is evident that 
these facts also point to the skate’s organ being in 
course of phylogenetic evolution. 
Again, it cannot be answered that the principle 
of correlation may be drawn upon in mitigation of 
the difficulty. The structure of the electric organ 
is far too elaborate, far too specialized, and far too 
obviously directed to a particular end, to admit of our 
conceivably supposing it due to any accidental corre- 
lation with structural changes going on elsewhere. 
Even as regards the initial changes of muscle-elements 
into electrical-elements, I do not think the principle 
of correlation can be reasonably adduced by way 
of explanation; for, as shown in the illustrations, 
even this initial change is most extraordinarily 
peculiar, elaborate, and specialized. But, be this as 
it may, I am perfectly certain that the principle of 
correlation cannot possibly be adduced to explain the 
subsequent association of these electrical elements into 
an electric battery, actuated by a special nervous me- 
chanism of enormous size and elaboration—unless, of 
course, the progress of such a structure were assumed 
to have been throughout of some utility. Under this 
supposition, however, the principle of correlation would 
be forsaken in favour of that of natural selection ; and 
we should again be in the presence of the same diffi- 
culty as that with which we started. 
But now, and further, if we do thus abandon corre- 
Bb 2 
