348 Darwin, and after Darwin. 
four different lines of descent—namely, the insects, 
reptiles, birds, and mammals. Now if in all, or in- 
deed in any, of these four cases the wings had been 
developed on the same anatomical pattern, so as not 
only to present the analogical resemblance which it is 
necessary that they should present in order to dis- 
charge their common function of flying, but likewise 
an homologous or structural resemblance, showing 
that they had been formed on the same anatomical 
“»lan,’—if such has been the case, I say, the theory 
of natural selection would certainly be destroyed. 
Now it has been alleged by competent naturalists 
that there are several such cases in organic nature. 
We have already noticed in a previous chapter 
(pp. 58, 59), that Mr. Mivart has instanced the eye 
of the cuttle-fish as not only analogous to, but also 
homologous with, the eye of a true fish—that is to 
say, the eye of a mollusk with the eye of a vertebrate. 
And he has also instanced the remarkable resemblance 
of a shrew to a mouse—that is, of an insectivorous 
mammal to a rodent—not to mention other cases. 
In the chapter alluded to these instances of homo- 
logy, alleged to occur in different branches of the tree 
of life, were considered with reference to the process 
of organic evolution as a fact: they are now being 
considered with reference to the agency of natural 
selection as a method. And just as in the former 
case it was shown, that if any such alleged instances 
could be proved, the proof would be fatal to the 
general theory of organic evolution by physical 
causes, so in the present casc, if this could be 
proved, it would be equally fatal to the mure spe- 
cial theory of natural selection. But, as we have 
