32 • ELIZABETH LOCKWOOD THOMPSON 



to feed freely during the first half of this period but was given 

 no food during the second half of the period. By thus controlling 

 the food an attempt was made to have all snails in the same 

 physiological state at the time of using them. 



6. As a me0,ns of detecting variations in the physiological state 

 a record was kept of the egg masses deposited by each snail, 

 but no relation was found between the egg laying activity and 

 any results of the experiments. 



7. Each snail was distinguished by a number painted on the 

 shell and a separate record was kept for each. 



8. After a preliminary series of experiments involving six 

 snails (Nos. 18-23), six other snails were used in the remaining 

 experiments. For two of these (4, 5) complete records are 

 presented in Tables II, III, IV, V, pp. 8, 13, 25 and 28. For 

 the remaining four (6, 7, 8, 14) a summar}^ of results is given 

 in Table VI, p. 30. 



9. Reactions of the mouth do not occur in the absence of ex- 

 ternal stimulation (preliminary test series). Six snails (Nos. 

 18-23, Table I, p. 6) were kept under observation for a total 

 period of 32.75 hours (an average of 5.47 hours each), without 

 stimulation. During this time but eight responses occurred 

 with a total of 38 reactions. Three of the responses were seen 

 to follow contact of the mouth of the snail with parts of the 

 mucous track left by the animal in its normal movements on 

 the surface film. The remaining five responses probably fol- 

 lowed similar contact with this nearly invisible mucus. For 

 experimental purposes the mouth response may be said to occur 

 only as the result of the external stimulation. It is " involun- 

 tary." The error introduced into later experiments as a result 

 of unobserved mucous stimulation is not enough to vitiate the 

 experiments. 



10. The normal food-rcspousc. — When food was applied to 

 the mouth and at once withdrawn response followed in 61% of 

 the tests (average for Snails 4 and 5). The average response 

 consisted of 3.93 reactions. The average time of reaction was 

 1.25 sec. or 46.2 reactions per minute. Table II, p. 8. 



11. The average number of reactions constituting the normal 

 food-response varied with the individual snail as follows; No. 4, 

 3.48; No. 5, 4.35; Nos. 6 and 7, 6.5; No. 8, 3.4; No. 14. 10.93. 

 The mean for all six snails is 5.86. 



