POLYGYRA ALBOLABRIS AND LIMAX MAXIMUS 273 



dence that Polygyrais possessed of sight, with the single ex- 

 ception that young individuals placed on a table, by a window, 

 seemed, to crawl away from the light, but in adult individuals the 

 light did not seem to make any difference. I have very frequently 

 moved a stick or some bright object directly in front of the ex- 

 tended tentacles, as the animal was moving, but with no effect 

 whatever. Often I have observed the animal running directly into 

 an object, withdrawing its tentacles and changing its course only 

 when the tentacles touched the object. 



Smell. That the snail possesses olfactory organs admits no dis- 

 pute,, but the location of these organs has been a matter of doubt. 

 J have had many snails in captivity for three years, and I have fre- 

 quently experimented with them to determine what degree of 

 olfactory sense they possess. After leaving them without food for 

 several days, I have put in one corner of the box a small head of 

 lettuce, concealing it by a few of the dead leaves. In a short time 

 the snails would appear from under the leaves, and on the surface 

 would raise the anterior portion of their bodies in the air, with 

 extended tentacles, turning from one side to the other, having ex- 

 actly the appearance of a quadruped sniffing the air in the en- 

 deavor to locate some object. Having decided on the position of 

 the lettuce, they would invariably move directly toward it, and 

 this sometimes from a distance of 18 inches. I have repeated this 

 experiment again and again but always with the same result. It 

 was impossible for the animals to see the lettuce on account of the 

 screen of leaves, and, as previously asserted, I am satisfied that 

 their power of vision is extremely limited, at least by daylight or 

 by artificial light. 



The discrimination in regard to food must be due also in a 

 great degree to the sense of smell. I have placed in my box of 

 snails young beet leaves, spinach and other tender vi^gelabk^s, 

 which it would naturally be supposed would be accei)table to the 

 snails; but they invariably refused to eat them, though deprived 

 of other food, and in no case were these articles even tasted, show- 

 ing, I think, that they were rejected on account of their odor. 



It being admitted that they possess olfactory organs, it remains 



