Criticisms of Theory of Natural Selection. 349 
before seen, no single case of this kind has ever been 
made out; and, therefore, not only does this sup- 
posed objection fall to the ground, but in so doing it 
furnishes an additional argument in favour of natural 
selection. For in the earlier chapter just alluded to 
I showed that this great and general fact of our no- 
where being able to find two homologous structures 
in different branches of the trce of life, was the 
strongest possible testimony in favour of the theory 
of evolution. And, by parity of reasoning, I now 
adduce it as equally strong evidence of natural selec- 
tion having been the cause of adaptive structures, 
independently developed in all the different lines of 
descent. For the alternative is between adaptations 
having been caused by natural selection or by super- 
natural design. Now, if adaptations were caused by 
natural selection, we can very well understand why 
they should never be homologous in different lines of 
descent, even in cases where they have been brought 
to be so closely analogous as to have deceived so 
good a naturalist as Mr. Mivart. Indeed, as I have 
already observed, so well can we understand this, 
that any single instance to the contrary would be 
sufficient to destroy the theory of natural selection zz 
toto, unless the structure be one of a very simple type. 
But on the other hand, it is impossible to suggest 
any rational explanation why, if all adaptations are 
due to supernatural design, such scrupulous care 
should have been taken never to allow homologous 
adaptations to occur in different divisions of the animal 
or vegetable kingdoms. Why, for instance, should 
the eye of a cuttle-fish ot have been constructed on 
the same ideal pattern as that of vertebrate? Or why, 
