232 BEHAVIOR OF THE LOWER ORGANISMS 



Here, however, the change of behavior of a given individual with a 

 change in these processes needs further investigation ; this has been 

 experimentally demonstrated only with reference to respiratory pro- 

 cesses in certain green organisms. In higher animals the dependence 

 of the behavior on the state of metabolism is of course most evident. 



This dependence of the reaction to stimuli on the relation of external 

 conditions to internal processes is a fact of capital importance, which 

 may furnish us a key to many phenomena that are obscure from other 

 standpoints. The processes of metabolism are not the only ones occur- 

 ring in organisms, and the relation of external conditions to other 

 internal processes may equally determine behavior. This is perhaps 

 the most fundamental principle for the understanding of the behavior 

 of organisms. 



Of a character differing from those just considered are certain 

 other factors which modify behavior in the ccelenterates. Past stimuli 

 received and past reactions given are, as in the Protozoa, important 

 determining factors in present behavior; they may cause either the 

 cessation of reaction to a given stimulus, or a complete change in the 

 character of the reaction. Certain simple conditions produce a ten- 

 dency in the organism to perform more readily an act previously performed 

 (p. 206). The internal state of the organism may be changed in most 

 varied ways, giving rise to corresponding changes in behavior. These 

 facts give behavior great complexity, as well as great regulative value* 

 even in so low a group as the one now under consideration. 



LITERATURE XI 



Behavior of Ccelenterata 



A. Behavior of Hydra: Wagxer, 1905; Wilson, 1891 ; Marshall, 1882; 

 Pearl, 1901 ; Mast, 1903; Tremblev, 1744. 



B. Behavior of sea anemones: Loeb, 1891, 1895, 1900; Nagel, 1892, 1894, 

 1894 «; Parker, 1896, 1905, 1905 a; Torrev, 1904; Jennings, 1905 a; Alla- 



BACH, I905; CARLGREN, I905 ; BURGER, I905. 



C. Behavior of hydroids : Torrey, 1904 a. 



D. Behavior of jellyfish : Romanes, 1885; Yerkes, 1902 a, 1902 b, 1903, 

 1904; Perkins, 1903; Bancroft, 1904; Loeb, 1900, 1900 a. 



