BAKER] EVENING WITH AQUARIUM AND SNAILERY 317 



heavier than its own bulk of water. If the needle is wet, or if it is 

 very large, it will not float, which shows that this film is very deli- 

 cate. If we place the glass holding the needle so that we can look 

 through the glass at the surface of the water, we will then see that 

 the needle rests in a little hollow, as if the water were covered with 

 a membrane." 



Among the pond snails were a number of orb snails carrying 

 their shells in a perpendicular manner, and waving their slender 

 tentacles about. Several of them were crawling along the bottom 

 of the tank, with a peculiar stepping motion. The animal pushed 

 its foot deep into the sand, the shell being drawn well down toward 

 the head. It was then pushed forward and upward, making a 

 little furrow, which prepared the way for another step. In this 

 way it ''stepped" along at a lively gait. We learned from Pro- 



A Carnivorous Land Snail A Common Land vSnail 



fessor Parker that this "stepping" was more for procuring food 

 than for locomotion. One of the large orb shells was crawling up 

 the side of the aquarium, eating everything in its path. Several 

 times a morsel was taken which proved distasteful to the animal, 

 and it was immediately "spit out." 



Some of the smaller snails, Amnicola and Valvata, were wander- 

 ing about, the former crawling with a wabbly gait, rolling the 

 shell from side to side. In another part of the aquarium, a number 

 of Physas were crawling rapidly along the bottom. Some of these 

 rose suddenly, Hke the pond snails. Others descended from the 

 top, suspended by a slender thread of mucus. Several of the pond 

 snails had crawled out of the water, and were attached to the glass, 

 a number of inches from the surface. Several apple snails, as well 

 as other members of the water breathers, were enjoying themselves 

 by crawling about the bottom, or on the sides of the aquarium, 

 apparently feeding; their long tentacles were waving, and their 

 blunt, cylindrical rostrum was moving about like the nose of a 

 hound on the scent. All of this animation in the aquarium made 

 it seem like a miniature world, as indeed it really was. 



