ALLIES OF THE PELECYPODA : MOLLUSCA 181 



every individual is likely to deposit eggs. The eggs may be 

 found on the branches of water-plants, or even on the per- 

 pendicular sides of a glass aquarium, imbedded in an ellip- 

 tical, clear, gelatinous mass from two millimeters to six 

 millimeters long. In each mass from five or six to twenty- 

 five eggs may be distinguished. 



The Land-Snail. One of the commonest of the land-snails in 

 America is the one shown in Fig. 93 (He'lix nebulo'sa). 'Like 

 its many kindred species of the genus Helix, it lives in 

 moist, protected places during the day, and comes out to 

 feed at night. Frequently it leaves its hiding-place in cloudy, 

 damp, but not in rainy, 

 weather. 



In general features, the 

 organs to be noted on the 

 exterior of this animal are 

 the same as in the pond- 

 snail. The openings of all 

 the internal organs 

 occur in the same 

 position in both 

 animals. There 

 are four tentacles 

 in Helix, an 

 upper, long pair 

 bearing the eyes, 

 and a lower, short 

 pair, which are 

 the organs of 

 touch. The edge of the mantle is thickened to form a collar. 



In the fall of the year, about the time of frost, the land- 

 snail ceases to eat, becomes inactive, and makes preparation 

 for the winter's sleep, or hibernation. Crawling to the pro- 

 tected side of an object which has a smooth surface, the 



FIG. 93. Living Land-Snail. Natural size 



