3 i o Problems of Organic Adaptation 



When we consider the wonderful efficiency of the living 

 machine in all of the respects named, is it any wonder that 

 there have always been those who have refused to believe 

 that it is really or only a machine? Is it any wonder that 

 they have insisted that it must be controlled by some sort 

 of indwelling intelligence? When we consider these remark- 

 able characteristics, we may well say in wonder and admira- 

 tion, "What a piece of work is a man!" or any other 

 organism. 



Such adaptations to general conditions of existence are 

 so common that to most persons they do not seem remark- 

 able, while some peculiar adaptation, such as the leaf-insect 

 or the Venus fly-trap, seems wonderful simply because it 

 is not common. Many of these more uncommon adaptations 

 have played an important part in the discussion of the vari- 

 ous theories of evolution which have been advanced during 

 the past century. As illustrations of adaptations to peculiar 

 conditions of life may be mentioned the fitness of horses' 

 limbs for running, those of seals for swimming, those of 

 birds for flight; or the adaptation of the long neck and fore 

 legs of the giraffe to its habit of browsing on trees; of the 

 long necks and legs of wading birds to their peculiar habits; 

 of the small fore legs and large hind legs and tail of the 

 kangaroo to its peculiar method of locomotion. In this con- 

 nection must also be considered the absence of limbs in 

 certain lizards, snakes, and amphibians, and the degenera- 

 tion or loss of wings in the apteryx and dinornis among birds 

 and in certain insects inhabiting stormy islands. Here also 

 must be classed the cases of adaptive atrophy or hyper- 

 trophy of organs, as for example the loss of eyes by cave 

 animals, the decreased size of the jaws and teeth of civi- 

 lized man as compared with savages, the increased size 

 and length of the middle digit, and the reduction or dis- 

 appearance of the lateral digits in ungulates, etc. 



