244 LESLIE B. AREY AND W. J. CROZIER 



Cocaine hydrochloride, atropine sulphate, and nicotine at M/lOO 

 concentration in sea-water stimulated very well the mouth, gills, and 

 the sole and edge of the foot. 



Chloretone M/200 in sea-water also stimulated these parts; but 



Urethane under the same conditions did not. 



Curare in saturated sea-water solution, gave rise to good, but not 

 pronounced responses. 



Urea. A M/10 solution, in rain water, did not lead to any clear 

 response on the part of the foot, and gave but weak responses from 

 mouth and gills. 



Ethyl and methyl alcohol solutions lOM, in rain-water, evoked reac- 

 tions from all parts save the mantle edge. With the methyl alcohol 

 the responses were slightly stronger, the gill retraction enduring about 

 twice as long (about 20 .sec, as compared with 8 to 10 sec. for the 

 ethyl); this may have been due to impurities; the ethyl alcohol was 

 especially pure. Full strength amyl alcohol induced responses as with 

 the two previous types, but considerably stronger movements resulted. 



It has been of interest to inquire if the surface of Chiton is 

 generally sensitive to sugars or to 'sweet' substances as a class. 

 In view of the usually high value of the limiting stimulating 

 concentration for sugars, it is necessary to consider the follow- 

 ing observations in the light of the subsequent experiments upon 

 osmotic excitation: 



Maltose: solutions M/3 or M/'IO, in sea-water, produced no clear 

 responses from any part. 



A IM solution in rain-water gave responses from mouth and gills 

 only. 



Sucrose: IM, in rain-water, led to no responses from the mouth 

 region, but gave good reactions from the ctenidia. 



M/3 in sea-water, gave general reactions from all parts. 



M/2, made by adding 1 volume of IM in rain-water to 1 volume of 

 sea-water, led to fair responses. 



M/3, made by adding 1 volume of IM in rain-water to 2 volumes of 

 sea-water, induced no reactions at all. 



Lactose: M/2 in rain-water gave strong responses everywhere except 

 at the mantle edge. 



d. To a variety of more obvious 'irritants,' the whole soft 

 ventral surface of Chiton reacts powerfully. Thus, H2O2 (3 per 

 cent) induces strong movements in all regions. Ether, chloro- 

 form, carbon bisulphide, aniline oil, and oils of cassia, juniper, 

 cloves, pennyroyal, thyme, bergamot, and origanum, when ap- 

 plied as a drop of the raw substance or in the form of a satu- 



