198 THE ORIGIN OF SPECIES 



which have penetrated into the earth from the geograph- 

 ically limited faunas of the adjacent tracts, and which, as 

 thej extended themselves into darkness, have been accom- 

 modated to surrounding circumstances. Animals not far 

 remote from ordinary forms, prepare the transition from 

 light to darkness. Next follow those that are constructed 

 for twilight; and, last of ail, those destiaed for total 

 darkness, and whose formation is quite peculiar." These 

 remarks of Schiddte's, it should be understood, apply not 

 to the same, but to distinct species. By the time that 

 an animal had reached, after numberless generations, the 

 deepest recesses, disuse will on this view have more or 

 less perfectly obliterated its eyes, and natural selection 

 will often have effected other changes, such as an in- 

 crease in the length of the antennae or pa'pi, as a com- 

 pensati.on for blindness. Notwithstanding such modifica- 

 tions, we might expect still to see in the cave-animals of 

 America affinities to the other inhabitants of that conti- 

 nent, and in those of Europe to the inhabitants of the 

 European continent. And this is the case with some of 

 the American cave-animals, as I hear from Professor 

 Dana; and some of the European cave-insects are very 

 closely allied to those of the surrounding country. It 

 would be difficult to give any rational explanation of the 

 affinities of the blind cave-animals to the other inhabi- 

 tants of the two continents on the ordinary view of their 

 independent creation. That several of the inhabitants of 

 the caves of the Old and New Worlds should be closely 

 related, we might expect from the well-known relation- 

 ship of most of their other productions. As a blind spe- 

 cies of Bathyscia is found in abundance on shady rocks 

 far from caves, the loss of vision in the cave-species of 



