Criticisms of Theory of Natitral 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 tree 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 in 

 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 not have been constructed on 

 the same ideal pattern as that of vertebrate ? Or why, 



