Reactions of ALolosoma to Chemical Stimuli 67 



reaction without any response being given by the anterior seg- 

 ments. 



e Different parts of the body are affected in different ways by 

 the same stimuhis. A given stimulus which may cause a well 

 coordinated negative reaction if applied at the anterior segment, 

 may inhibit coordinated movement if applied at the middle seg- 

 ments of the body. 



/ Any interference with the integrity of the nervous system 

 seriously interferes with the power of coordinated movement. 



g Physical changes in the environment, due to variations in 

 the relative amount of light and heat pervading it, produce an 

 effect upon the animal economy equivalent to the effect produced 

 by different concentrations in the chemicals used in these experi- 

 ments. 



Results with Strong Stimuli (chemicals very strong., see p. 63) 



a Reactions to chemicals of this order, when applied to the 

 anterior end consist of a vigorous refiex movement which throws 

 that end away from the field of stimulation. The anmial may 

 then exercise its powers of locomotion and escape. 



b When these chemicals are applied to any other part of the 

 body the reflexes are of such a nature as to inhibit coordinated 

 movement away from the stimulus. 



c Interference with the integrity of the nervous system does not 

 seriously modify the type of reaction developed by these solutions. 



d The energy imparted to the animal by these chemicals may 

 be directly accentuated by an increase in the relative amount of 

 light or heat pervading the ambient medium. 



c The relative toxicity of these solutions depends largely upon 

 the age of the part impinged, and also upon the physiological con- 

 dition of the organism as a whole. 



CONCLUSIONS 



By means of the localized application of different chemicals with 

 varying concentration we have stimulated in yEolosoma charac- 

 teristic movements designated as the action system. This shows 



