350 Darwin, and after Darwin. 
among the thousands of vertebrated species, should no 
one of their eyes be constructed on the ideal pattern 
that was devised for the cuttle-fish? Of course it may 
be answered that perhaps there was some hidden reason 
why the design should never have allowed an adapta- 
tion which it had devised for one division of organic 
nature to appear in another—even in cases where the 
new design necessitated the closest possible resem- 
blance in everything else, save in the matter of anatomi- 
cal homology. Undoubtedly such may have been the 
case—or rather such mzzs¢ have been the case—if the 
theory of special design is true. But where the ques- 
tion is as to the truth of this theory, I think there can 
be no doubt that its rival gains an enormous advan- 
tage by being able to exp/ain why the facts are such 
as they are, instead of being obliged to take refuge 
in hypothetical possibilities of a confessedly unsub- 
stantiated and apparently unsubstantial kind. 
Therefore, as far as this objection to the theory of 
natural selection is concerned—or the allegation that 
homologous structures occur in different divisions of 
organic nature—not only does it fall to the ground, 
but positively becomes itself converted into one of the 
strongest arguments in favour of the theory. As 
soon as the allegation is found to be baseless, the 
very fact that it cannot be brought to bear upon any 
one of all the millions of adaptive structures in 
organic nature becomes a fact of vast significance on 
the opposite side. 
The next difficulty to which I shall allude is that 
of explaining by the theory of natural selection the 
preservation of the first beginnings of structures which 
