Adaptation 63 



contrary instinct. This moth does not fly away from danger, but 

 " feigns death," that is, it draws antennae, legs and wings close to the 

 body, and remains perfectly motionless. It may be touched, picked 

 up, and thrown down again, and still it does not move. This remark- 

 able instinct must surely have developed simultaneously with the 

 wood-colouring; at all events, both cooperating variations are now 

 present, and prove that both the external and the most minute 

 internal structure have undergone a process of adaptation. 



The case is the same with all structural variations of animal 

 parts, which are not absolutely insignificant. When the insects 

 acquired wings they must also have acquired the mechanism with 

 which to move them the musculature, and the nervous apparatus 

 necessary for its automatic regulation. All instincts depend upon 

 compound reflex mechanisms and are just as indispensable as the 

 parts they have to set in motion, and all may have arisen through 

 processes of selection if the reasons which I have elsewhere given for 

 this view are correct 1 . 



Thus there is no lack of adaptations within the organism, and 

 particularly in its most important and complicated parts, so that we may 

 say that there is no actively functional organ that has not undergone 

 a process of adaptation relative to its function and the requirements 

 of the organism. Not only is every gland structurally adapted, down 

 to the very minutest histological details, to its function, but the 

 function is equally minutely adapted to the needs of the body. 

 Every cell in the mucous lining of the intestine is exactly regulated 

 in its relation to the different nutritive substances, and behaves in 

 quite a different way towards the fats, and towards nitrogenous 

 substances, or peptones. 



I have elsewhere called attention to the many adaptations of the 

 whale to the surrounding medium, and have pointed out what has 

 long been known, but is not universally admitted, even now that in 

 it a great number of important organs have been transformed in 

 adaptation to the peculiar conditions of aquatic life, although the 

 ancestors of the whale must have lived, like other hair-covered 

 mammals, on laud. I cited a number of these transformations the 

 fish-like form of the body, the hairlessness of the skin, the trans- 

 formation of the fore-limbs to fins, the disappearance of the hind- 

 limbs and the development of a tail fin, the layer of blubber under 

 the skin, which affords the protection from cold necessary to a warm- 

 blooded animal, the disappearance of the ear-muscles and the auditory 

 passages, the displacement of the external nares to the forehead for 

 the greater security of the breathing-hole during the brief appearance 

 at the surface, and certain remarkable changes in the respiratory and 

 circulatory organs which enable the animal to remain for a long time 



1 The Evolution Theory, London, 1904, p. 144. 



