4248 Molhisks. 



be protracted to a far longer period. It is most probable that many- 

 will differ from me in opinion, and perhaps some will ridicule the 

 idea : if they can discover any other probable or even possible means 

 of accounting for the presence of the bat in the vault, exclusive of a 

 crack or chink in it, or of its having been opened within the memory 

 of living man, both of which views I firmly oppose, I shall feel greatly 

 obliged by their stating their opinions in the ' Zoologist : ' meanwhile 

 I hold to my belief, that the bat had been there for not less than one 

 hundred and six years ! 



Alfred Charles Smith. 

 Yatesbury Rectory, Calne, 

 February 18, 1854. 



Note on the habits of Lymncea stagnalis. — This fresh-water mollusk is long-lived in 

 confinement. I have had some in glass jars since the early part of last summer. To- 

 day I had a good opportunity of observing their mode of respiration. As one of them 

 lay floating on the surface of the water, upheld by the air in its pulmonary sac, and 

 by its inverted hollowed boat-like foot, I dropped a morsel of table salt on the centre 

 of the latter. Instantly the animal retracted, falling heavily to the bottom, giving 

 out while doing so, and for some seconds after, a stream of air from its breathing ori- 

 fice under the mantle on the edge of the last whorl of the shell. It lay at the bottom 

 for a few minutes in a kind of convulsion, projecting its one tooth to an unusual ex- 

 tent. It then became an interesting thing to notice how anxious it appeared to reach 

 the surface for more air, how slowly it crept up the side of the glass, and how many 

 times it fell down again, in consequence of its greater specific gravity than when under 

 its usual conditions. At length it attained the top of the water. Here, instead of 

 conforming to its usual habit of throwing itself, freely detached, swimming foot up- 

 ward, as at first described, it crept further up the glass, half-an-inch above the water- 

 line, in fact, until it had exposed its respiratory hole to the air. Then it took in a 

 supply of the elastic fluid, the edge of the mantle opening with a slight, but distinct 

 sound while in the act, and resumed its ordinary functions, remaining detached at 

 the surface, as before. The evident reason for thus departing from its usual course, 

 was, that its instinct led it to be aware that its weight was increased by the previous 

 expulsion of air, and that it had lost its flotive powers. I repeated the experiment in 

 the course of an hour, but not with quite the same result as before, for now the ani- 

 mal was so much weakened by its previous treatment, that I had to expose it to the 

 atmosphere to save its life. It is now (February 4th) quite healthy and active. 

 These observations give me much encouragement to proceed in minute and constant 

 examinations, even when the subjects of them are the commonest inhabitants of our 

 ditches. — William Alford Lloyd; St. John's Square, Clerkenwell, London, February 

 4, 1854. 



