54 H. G. Krihs 



cinths in battery jars filled with fresh water. In a few days 

 large numbers of the ^olosoma migh t be observed during the early 

 hours of the day, crawling about the sides of the jars. 



There were a number of suggestive differences noted between 

 these two species in their reactions to changes in the relative 

 amount of light, moisture, and temperature pervading the ambient 

 medium. These phenomena will be considered in another paper. 

 At present our purpose is to work out the main features of the 

 action system as shown in both species under the influence of 

 external stimuli. We examine first the reactions to chemicals for 

 the reason that with them it is easy to control and stimulate all 

 the movements normally exhibited in the action system, and thus 

 to observe the mechanism of the response. 



REACTIONS TO CHEMICAL STIMULI 



Methods 



A graded series ot experiments was made with the following 

 chem.icals: 



1 Mineral acids: HCL, H,SO„ HNO3 



2 Organic acids: HCoHjO., (acetic), H..C,Oj (oxalic), 

 H3CeHA (citric). 



3 Hydrates: KOH, NaOH. 



4 Carbonates: K3CO,, Na,C03. 



5 Halides: KCl, KBr, NaCl, NaBr. 



6 Sulphates: FeSO„CuSO„ ZnSO,. 



The acids and alkalies were titrated to standard normal solu- 

 tions (n). The salts were prepared in gram-molecular solutions 

 (m). The first series of experiments were made by allowing the 

 chemical stimulus to flow toward the animal through a fine capil- 

 lary pipette, the conducting tube of which had an inside diameter 

 of 0.3 mm. the bulb holding about \ cc. of the fluid, with an air tube 

 a trifle larger than the conducting tube. The orifice of the con- 

 ducting tube was placed about ^, mm. from the part to be stimu- 

 lated. Localized applications of the chemical were thus made at 

 the head segment, at the caudal segment, and finally upon the 

 middle segment of the body. 



