344 FOUNDATIONS OF BIOLOGY 



a nicety of adaptation of behavior to environmental condi- 

 tions that otherwise would be impossible that it is our 

 chief means of adaptation "it is a grave mistake to mini- 

 mize the importance of the great gulf between Man's nature 

 and that of the most highly developed of the lower animals. 

 In no respect are these differences more marked than in the 

 various forms of learning that, taken together, form the 

 means of education." (Cameron.) 



Thus it is clear that, with all the variations in structure and 

 function, organisms all possess irritability in common: they 

 all exhibit adaptive responses which enable them to exist in 

 spite of surrounding changes. "Adaptability appears to be 

 the touchstone with which nature has tested each kind of 

 organism evolved; it has been the yard-stick with which she 

 has measured each animal type; it has been the counter- 

 weight against which she had balanced each of her produc- 

 tions . . . the general course of evolution has been always 

 in the direction of increasing adaptability or increasing per- 

 fection of irritability." (Mathews.) The individual's heri- 

 tage affords the cumulative result of the adaptations of the 

 race including adaptability. 



