302 W. J. CROZIER AND LESLIE B. AREY 



b. Substances of the sugar group are quite ineffective for 

 chemical stimulation of the body surface. Maltose and sucrose 

 solutions, 1 M in rain-water, or saturated lactose solutions 

 (0.5 M=^) induced no response. Glycerin, 2 M and 3 M, was 

 reacted to by all portions of the surface; more dilute solutions 

 were ineffective; stimulation was in this case of osmotic origin. 



Solutions of several alkaloids: cocaine (0.01 M), nicotine 

 (0.03 M), and weak solutions of curare gave very sUght activa- 

 tions; atropine sulphate (0.01 M) was quite stimulating. Solu- 

 tions of urea (0.1 M) and of urethane (0.005 M) hkewise failed 

 to stimulate, although chloretone (0.005 M) gave good responses 

 from all parts. These solutions were made up in sea-water. As 

 a whole, the alkaloids and narcotics were relatively inefficient 

 for activation. 



The following substances were found capable of producing 

 sensory activation: neutral salts, various acids, KOH, ethyl 

 alcohol (0.1 M), irritants such as H2O2, and various essential 

 oils. These substances, in appropriate concentration, led to 

 pronounced reactions involving the whole body. 



In the characteristic features of their activation, no less than 

 in the variety of substances to which reaction is given, the gen- 

 erally distributed chemical sense of Chromodoris resembles that 

 of other marine animals (Arey and Crozier, '19). Thus in 0.625 

 M solution in rain-water, the chlorides of the alkalies are effective 

 in the following order: 



NaCl Very weak responses:. 



IMild responses, chiefly trom the 'rhinophores' and oral tentacles. 

 The remainder of the general surface but weakly reactive; no 

 clear differences obtainable between the effects of these two 

 salts. 

 KCl Extremely strong reactions from all regions. 



From the relative vigor of the responses attending stimulation 

 of the mouth region and of the 'rhinophores,' the cation order of 

 efficiency is 



K>NH, Li>Na. 



The stimulation here is primarily a matter of the cation. KCl, 

 KB, KI, and KNO3 lead to equally strong reactions from all 



