THE EDUCABILITY OF A SNAIL 59 



haved. For what captured specimens very gener- 

 ally do on the slightest provocation even jarring 

 the aquarium a little is to expel the air from their 

 breathing chamber, retract into their shell, and drop 

 to the bottom, where they may sulk for an hour. 

 Realizing that this nervousness would make ex- 

 perimenting impossible, Miss Thompson began by 

 "taming" her captives. They were taken in the 

 hand at intervals and moved about under water; 

 they were held till they protruded from the shell; 

 they were abundantly handled, till they became so 

 accustomed to it that they could be touched by the 

 observer, or moved from one dish to another, with- 

 out retracting their body or expelling the air from 

 their lung. This " taming " is a further evidence of 

 adaptability. 



Very interesting data as to the educability of 

 animals have been obtained by using simple laby- 

 rinths in which the creatures are placed at repeated 

 intervals to see whether they learn to get out more 

 quickly in the course of experience. It has been 

 found useful in many cases to reward, say with 

 food, a rapidly successful solution of the labyrinth, 

 and to punish, say with a slight electric shock, the 

 taking of the wrong road. Most of these experi- 

 ments have been made with animals of high degree 

 like cats and mice ; Miss Thompson has spent much 

 time and ingenuity in inquiring whether the laby- 

 rinth experiment can be adjusted so as to apply to 

 freshwater snails. In one form of the experiment 

 a Y-shaped cylindrical glass tube was anchored 



