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 A\\ the responses of germ 



FIG. 16, a, b, c. REPULSION OF Spirilla BY COMMON SALT, a, condition 

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



x, y, z, 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 z, the bacteria have 

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



