1 84 THE DOCTRINE OF DESCENT. 



life. " In South America a burrowing rodent, the Tuco- 

 tuco, or Ctenomys, is even more subterranean in its 

 habits than the mole; and I was assured by a Spaniard, 

 who had often caught them, that they were frequently 

 blind; one which I kept alive was certainly in this con- 

 dition, the cause, as appeared <5n dissection, having been 

 the inflammation of the nictilating membrane. As fre- 

 quent inflammation of the eyes must be injurious to any 

 animal, and as eyes are certainly not necessary to ani- 

 mals having subterranean habits, a reduction in their 

 size, with the adhesion of the eyelids and growth of fur 

 over them, might in such case be an advantage; and, 

 if so, natural selection would constantly aid the effects of 

 disuse." 



In the classes of flying animals, a large number have 

 left off flying; and we find their flying apparatus in an 

 aborted or incomplete condition, which perverse judg- 

 ment and reasoning alone can regard as a state of pro- 

 gressive development from yet simpler rudiments. If 

 throughout the great family of the Coleoptera, genera 

 and species are to be found with imperfect flying ap- 

 paratus, consolidated wing covers, &c., if the whole fam- 

 ily of Staphylinse does not possess the power of flight, 

 no one dreams of considering them as arrested forms; 

 but it is conceivable that the mode of life in which they 

 differ from the other members of their order and class, 

 gradually superinduced in their flying ancestry the habit 

 of not flying, and at the same time the atrophy of the 

 organs of flight. With this was combined, as these 

 beetles show, no degradation of organization, but, on 

 the contrary, a higher and extremely advantageous de- 

 velopment of other organs, the manducatory and loco- 



