656 RAYMOND PEARL. 



seen that this org-au bent directly towards tlio mouth of the 

 capillar}'. The pharynx oriented itself with refei-ence to the 

 issuing chemical. 



The cases in which specimens were "indifferent" to this 

 solution (i. e. did not give either the positive or negative re- 

 action) were evidently not due to the fact that the animal 

 was not stimulated, but", on the contrary, that it was stimu- 

 lated about equally to negative and positive responses. This 

 was indicated by their restless behaviour when '^ indifferent." 

 While the animal as a whole moves in a straight line, the 

 head constantly moves slightly towards and away from the 

 stimulus. Evidently the solution is not quite strong enough 

 to induce a definite negative reaction, nor cjuite weak enough 

 to cause a clear positive response. 



-^jy per cent,, -j^y per cent., and J^ per cent. — Distinct posi- 

 tive reaction in all cases. 



■jjrjj per cent. — Positive reactions in some cases, mainly 

 indifferent. The "indifference" is now due to lack of 

 stimulation. 



Below Yiii) psi' cent. I have been unable to get definite 

 responses of any sort with KCl. 



Magnesium Chloride, i per cent. — Usually sharp 

 negative reaction. In some cases a slight turn towards the 

 stimulus preceded the negative response, and in some few 

 other trials the animal Avas indifferent. 



Y^ij per cent. — Weaker negative reaction. In one case 

 clear positive reaction. No local contraction of the region 

 stimulated is caused by this chemical. 



"aV P^^' cent. — Positive reaction in all cases. Complete 

 food i-eaction could be induced. 



-j\j per cent. — Weak positive reaction or indifferent. 



Suiumary. — To the salts NaCl, NaBr, KCl, and MgCL 

 the phinarians react as to other chemicals, by giving the 

 negative response to strong concentrations and the positive 

 to weak. 



Cane-sugar. — Sugar solutions, in all concentrations 

 above -j',, ]ior ceut., so far as I liave l)een able to discover, 



