354 EVOLUTION, GENETICS, AND EUGENICS 



Thus, the eyes of the new-born infant are essentially finished mech- 

 anisms before they ever function as organs of vision. They cannot 

 therefore have been molded for their visual function by functioning 

 in a visual manner. Of course they must have been functioning in 

 some way, as all living protoplasm must function, but they cannot 

 have functioned in a way that would in itself account for the fact that 

 the eye is a very intricate optic mechanism. Similarly, the human 

 infant has good lungs and good vocal cords before it ever takes the 

 first breath of air or gives the first cry. Such adaptive structures as 

 these are said to be racial or inherited adaptations. Any theory of 

 evolution worthy of the name must account for the origin and per- 

 petuation of such inborn adaptations. It was partly to explain the 

 origin and perfection of adaptations such as these that Lamarck pro- 

 posed his theory of the inheritance of acquired characters and Charles 

 Darwin devised his theory of natural selection. It is still unsettled as 

 to which of these theories is the more adequate, but the consensus of 

 expert opinion favors Darwin's explanation. 



It would be impossible to give any comprehensive account of ani 

 mal or of plant adaptations in the brief space of such a chapter as this. 

 Let it suffice to classify adaptations and to describe a few representa- 

 tive adaptations, confining our attention to those which are obvious- 

 ly racial or inherited in character. 



ADAPTATIONS CLASSIFIED 



Adaptations are variously classified by different authors,- and that 

 of Jordan and Kellogg is as good as any: "(a) food-securing; (b) self- 

 defense; (c) defense of young; (d) rivalry; (e) adjustment to sur- 

 roundings." 



Some very common adaptations may belong to several of these 

 categories at once. Thus the sharp teeth and hooked claws of car- 

 nivorous mammals serve equally well for food-securing, for self- 

 defense, for defense of young, and for rivalry. Similarly, the horns 

 of deer and other ungulates are equally adapted for self-defense, 

 defense of young, and rivalry. 



There can be no especial advantage, in this connection, in present- 

 ing a detailed review of adaptations of the sorts given in the foregoing 

 classification; therefore we shall confine our efforts to a description 

 of a few typical adaptations about which the greatest controversy 

 has raged. 



