112 RAMANAN : ON THK HABITS OF AMPULLARIA. 



at the bottom of the aquarium ami put it suddenly in hot water, it gives oii 

 a series of bubbles before dying. The same thing also happens in the case 

 of an animal which has been long out of water. An interesting point in 

 the animal's ascent is that it is able, despite its bulk, to trust itself safely 

 to the very delicate stems or leaves of aquatic plants. These never bend 

 or move from side to side when it is ascending, and it is j)robable that its ex- 

 panded condition contributes to the feat. The plants are so thin that, but 

 for the elaborate hydrostatic adjustment of the animal in spreading out 

 its body, they would otherwise bend or give way under the weight of 

 such a heavy body. We must at the same time remember that the animal 

 uses its discretion in making a distinction as to its manner of movement, 

 whether it shall crawl up hard objects, such as the inner side of the aquar- 

 ium, stones, etc., or ascend the flexible stems of aquatic plants. In the one 

 case, it keeps its foot and tentacles normally spread out, while in the other 

 it produces them to an extraordinary extent, and keeps the body greatly 

 expanded in order to lessen its weight in the water as far as possible, and 

 in order to ascend the leaves of the most delicate and fragile plants, without 

 swaying to one side or the other. In such cases it is easy to observe the 

 laborious caution the animal takes, lest it sliould slip down. I have found 

 in the aquarium AmpuUarians ascending clusters of leaves as easily as single 

 ones. When they ascend collections of leaves, they do so without difliculty. 

 But when they climb a single leaf or stem, they take the utmost precaution, 

 expand their bodies to the greatest limit, and progress gradually. But 

 the most interesting point of all, lies in their careful efforts to extend the 

 foot into a thin leafy expansion and engulf the long narrow leaf or stem 

 within it. 



And now marshalling, in conclusion, all the facts we have been able 

 to gather respecting Ampullarian locomotion in water, we get three groups 

 of phenomena, which may be put as follows :— - 



I. — Floating on the Surface of the Water. 



(A.) Active. — Body thoroughly extended or only extended partially. 

 Goes down when disturbed. 



(B.) Passive. — Body only partially extended. Nothing short of a sharp 

 prick will make the animal close the operculum and sink. A hard 

 knock on the shell with a heavy nail, sends it down, but as soon 

 as the impulse is exhausted, it floats. The animal behaves like a 

 dried cork immersed in water. 



II. — Descending to the Bottom by 



(A.) Sinking. — By suddenly withdrawing all the soft parts, closing the 

 operculum and giving off a series of bubbles. This may either be 

 (i) Voluntary, or (ii) Involuntary, when necessitated by any 

 external interference or injury. 



