STIMULATIONS IN NUDIBRANCHIATE MOLLUSKS 427 



Chemical stimulation. As shown per the accompanying tables 

 (pp. 433-438), a number of chemical solutions of different con- 

 centrations were applied to the various parts of the body by the 

 capillary-pipette method. This pipette was sealed at one end and 

 insulated around the middle by a cork, for manipulation purposes. 

 The same amount of the particular chemical used (unless stated 

 differently) was applied each time. The pipette was rinsed exter- 

 nally each time after refilling to avoid diffusion of the cheixdcal so- 

 lution in the medium of the specimen experimented on and in order 

 to secure as nearly as possible the normal condition of the sea- 

 water. Sixty-two animals were used. Each one was placed in 

 a finger-bowl half filled with fresh sea-water, and the pipette then 

 applied with the chemical solution so as not to touch the body 

 with the pipette, but to allow only the chemical solution in 

 question to pass onto the desired part of the body. Solutions 

 heavier than sea-water were allowed to flow from above; those 

 lighter than sea-water were applied to the animal when it was 

 crawling on the surface film of the water or on the side of the 

 vessel. 



The following signs represent the relative degrees of modes of 

 response to the stimuli: the negative sign represents an attempt 

 to avoid the stimuli. There are five of this kind, three positive 

 and three others as explained below : 



1. — g, means general but a slow reaction with an attempt to 

 avoid the stimulus. 



2. — , means a more definite negative response. 



3. , means a still more definite negative response. 



4. , means explosive negative response. 



5. , means explosive negative response, violent con- 

 tractions and twistings of the body or parts of it. 



6. The plus signs, +, ++, and + + +, mean various degrees 

 of positive response with an attempt to move in the direction of, 

 or toward the stimuli. 



7. 0, means no reactions. 



8. ®, means indefinite reaction which shows no particular 

 effort to avoid the stimulus. 



9. G, means indefinite reaction but rather with opposite 

 direction to ©. 



