RAMAN AN : ON THE HABITS OF AMPULLARIA. Ill 



trips to land, it may either be found crawling or at rest with the operculum 

 closed. If it should be crawling, it keeps the siphon fully expanded, 

 and breathes air. We can at the same time see the circular aperture in 

 the lower wall of the pulmonary sac, opening and contracting, as well as 

 the siphonal orifice in rapid alternation. The contractions and expansions 

 taken together average 12 a minute. The expansion is twice as rapid 

 as the contraction. When it is at rest, it is difficult to say if it breathes or 

 not (see note above). Both in this condition and in that mentioned in foot- 

 note 5, it is almost certain that metabolism is very low, and that respiration, 

 if any, is extremely feeble. The operculum is so hermetically closed that 

 no air can possibly get in. 



I have occasionally seen the animal floating on the surface of the water, 

 with its foot and tentacles spread out. When in this posture, it keeps its 

 siphonal orifice closely shut without exhibiting either sort of breathing. 

 There is no doubt that in order to float like this the animal must, in the 

 first instance, fill its pallial cavity with air. And that this is actually the 

 case, I have ascertained by giving a severe blow with the finger on the 

 shell, when the animal was floating at ease. It at once went down on 

 account of the blow, and as it sank, gave off a series of bubbles which 

 burst as soon as they reached the surface, thus proving the presence of air 

 in the mantle-cavity. 



If we do not, on the other hand, disturb the animal when it indulges 

 in this indolent floating, after 10 minutes or more, it either attaches itself 

 to some plant or other object near at hand, and begins taking in air or 

 water, or sinks to the bottom with its foot fully extended, its tentacles spread 

 out, and its elongated siphon closed. I did not find the slightest alteration 

 of form in the tentacles, siphon or foot. No bubbles of air are given off 

 either when it reaches the bottom or afterwards. 



The animal, strange to say, is not able to float from the bottom to 

 the surface, however extended it may keep its body, showing thereby 

 that it is not able to displace a sufficient volume of water to proportionately 

 lessen its weight. This fact seems to contradict my first observation that 

 the animal in a fully expanded state is able to float on the surface of the 

 water, and I am unable to explain the apparent discrepancy. 



Thus, whenever the Ampullarian wants to ascend to the surface, it 

 invariably crawls, but when descending, it may either crawl, fall straight- 

 way to the bottom after closing its operculum, or, more rarely, may float 

 down. Whenever the animal falls, by suddenly closing its operculum, 

 either voluntarily or on account of interference, bubbles of air are given oft' ; 

 but not when it era wis or slowly sinks down. Of course, the animal, when 

 roaming undisturbed under water, gives oft" now and then one or two 

 bubbles (foot-note 5) ; and these are to be carefully distinguished from 

 the scries of bubbles given oft by the animal, when it is forcibly pushed 

 down. There is httle doubt that the Ampullarian keeps within its body 

 some air for pneumatic needs. If we take, for instance, an animal lying 



