82 JEAN DAWSON 



were seen scraping the sides of the dish. This quiet period 

 did not last over an hour or so, the -time varying with the in- 

 dividual snail, then they were seen to again give the food re- 

 flex. It was found that any mechanical stimulus, such as a 

 glass rod touched to the head or mouth, or bits of chalk would 

 start the action of the jaws. At the end of four or five days 

 of fasting, the snails could not be turned around on the film 

 or disturbed without causing the jaws to open and close and 

 to continue to do so for long periods of time. If the temperature 

 of the water was raised a few degrees, it seemed to make the 

 snails much more ravenous so that they moved about with 

 increased activity and opened their mouths wider, showing a 

 greatly increased food reaction. 



1. When the snail was brought to the film for study it was 

 usually giving the food reflex. If now a grain of sugar was 

 placed upon its mouth, the snail responded by an increased 

 opening of the mouth and a raising of the head. 



2. If upon the mouth of another snail acid instead of sugar 

 was placed, the animal at once responded by increased action 

 of the jaw and a raising of the head. The animal behaved 

 for the first three or four minutes in just the same way that 

 it did tow'ard the sugar. Absolutely' no difference could be 

 seen between its behavior and that of the sugar fed snail unless 

 a large drop of acid was given, in which case the snail drew its 

 head back into its shell, but came up to the film directly and 

 took in the acid as before. After the first three or four minutes 

 the snail closed the mouth for longer and longer periods of time, 

 if the acid was applied every time the reflex started. 



3. Now, if the acid was given a hungry snail for five minutes 

 and then sugar gi\'en, the snail did not respond immediately 

 as when given sugar at first. If another snail was fed acid 

 fifteen minutes, i. e., whenever the reflex started, it took longer 

 for it to respond to the sugar than it did when the acid was fed 

 but five minutes. This period of indifference to the sugar 

 increased as the time of feeding acid was increased. In one case 

 acid was touched to the mouth of the snail for an hour every 

 time the animal began the food reflex; it then took over four 

 hours for the animal to open its mouth to sugar although its 

 mouth was continually bathed in it during this time. 



■4. If sugar w^as given first, then acid applied, the snail ate 



