Facts and Factors of Development 



39 



becomes differential sensitivity and special senses in the process 

 of embryonic differentiation. Such sensitivity is the basis of all 

 psychic processes ; sensations are the elements of the mind. 



2. Reflexes, Tropisms, Instincts. All the responses of germ 



FIG. 1 6, a, b, c. REPULSION OF Spirilla BY COMMON SALT, a, condition 

 immediately after adding crystals ; b and c t later stages in the reaction. 



.r, v, s, repulsion of Spirilla by distilled water. The upper drop consists 

 of sea-water containing Spirilla, the lower drop, of distilled water. At x 

 these have just been united by a narrow neck; at y and 2, the bacteria have 

 retreated before the distilled water. (From Jennings, after Massart.) 



