EVOLUTION OF PROTOZOA 



113 



neighborhood of a wave-length of 477 /iyu, and (2) in the 

 yellowish-green, in the region of X = 534 /u/a; and these two 

 wave-lengths affect different organisms, with no very evident 

 relation to the nature of these latter. Thus the blue rays 

 (of 477 ixfx) attract the protozoan flagellate Euglena, the hydroid 



HEAT 



Billion ■vibraiijlds per second'-i^^'^ 



CHEMICAL 



ULTRA VIOLET 



Fig. 17. Light, Heat, and Chemical Influence of the Sun. 



Diagram showing the increase, maximum, and decrease of heat, light, and chemical 

 energy derived from the sun. The shaded area represents that portion of the spec- 

 trum included in the phosphorescent light emitted by our common fire-flies. It is 

 probable that it corresponds more closely with the light sensitiveness of the fire-fly's 

 eye than with that of the human eye as represented by the wave marked "Light." 

 After Ulric Dahlgren. 



coelenterate Eudendrium, and the seedlings of oats; while the 

 yellowish-green rays (of 534 /x^i) in turn affect the protozoan 

 Chlamydomonas, the crustacean Daphnia, and the crustacean 

 larvae of barnacles. 



Aside from these heliotropic movements which they share 

 with plants, animals show higher powers of individuality, of 

 initiation, of experiment, and of what Jennings cautiously 

 terms "a conscious aspect of behavior." In his remarkable 

 studies this author traces the genesis of animal behavior to 



