Critectsms of Theory of Natural Selection. 365 
—namely, the case of an adaptive organ the genesis of 
which could not possibly be attributed to natural selec- 
tion, and must therefore be attributed to supernatural 
design. Now, I do not deny that he is here in pos- 
session of an admirable case—a case, indeed, so ad- 
mirable that it almost seems to have been specially 
designed for the discomfiture of Darwinians. There- 
fore, in order to do it full justice, I will show that it is 
even more formidable than the Duke of Argyll has 
represented. 
Electric organs are known to occur in several widely 
different kinds of fish—such as the Gymnotus and 
Torpedo. Wherever these organs do occur,’ they 
perform the function of electric batteries in storing 
and discharging electricity in the form of more or less 
powerful shocks. Here, then, we have a function 
which is of obvious use to the fish for purposes both 
of offence and defence. These organs are everywhere 
composed of a transformation of muscular, together 
with an enormous development of nervous tissue; 
but inasmuch as they occupy different positions, and 
are also in other respects dissimilar in the different 
zoological groups of fishes where they occur, no diffi- 
culty can be alleged as to these analogous organs 
being likewise homologous in different divisions of the 
aquatic vertebrata. 
Now, in the particular case of the skate, the organ 
is situated in the tail, where it is of a spindle-like 
form, measuring, in a large fish, about two feet in 
length by about an inch in diameter at the middle of 
the spindle. Although its structure is throughout 
as complex and perfect as that of the electric organ in 
Gymnotus or T. orpedo, its smaller size does not admit 
