Mollttsks. 5371 



and on March 7th, 1850, it was observed that he must have come out of* 

 his shell in the interval (as the paper had been discoloured, apparently 

 in his attempt to get away) ; but, finding escape impossible, had again 

 retired, closing his aperture with the usual glistening film ; this led to his 

 immersion in tepid water, and marvellous recovery." To the instance 

 mentioned by Mr. Woodward I may add two from my own observa- 

 tion. In August, 1852, 1 collected some specimens of Helix sylvatica 

 at Sion, in the valley of the Rhone ; on removing them from the chip 

 box in which they had been placed, a year and a half afterwards, the 

 majority of them were found to be still alive. While now writing I 

 have a Helix aspersa near me which certainly has not tasted food 

 since March, and as it was captured the first spring day that I had 

 seen one of his race abroad, it seems highly probable that he has not 

 had more than a single meal (if he had had time to get that) for nearly 

 a year, since H. aspersa usually retires to hybridate about this time, 

 at any rate in this cold part of the country. I therefore do not con- 

 sider the abstinence from food of the Mollusca in the bottle to be 

 anything novel. 



The second point to be noticed is, however, of great importance, — 

 the fact that these animals lived during such a lengthened period 

 without any oxygen being supplied to them. It is not a little 

 remarkable that the pulmonated Limneus stagnalis, which breathe the 

 air by means of lungs, were unable to find a sufficient amount of 

 oxygen in the air confined between the water and the cork (about one- 

 third of the volume of the bottle) to support life, and at once died, 

 whereas the Valvatae and Bithinia, though more than double the Limnei 

 in number, were able, by means of their branchice, to extract a suffi- 

 cient quantity of oxygen from the water for respiration during a con- 

 siderable period of time, and that some of them lived for a whole year. 

 I do not see how any additional supply of oxygen could have been 

 imparted to the water after it had been placed in the bottle ; the. small 

 piece of leaf, a mi>re atom, even if growing under favourable circum- 

 stances, could have aerated the water to but a very trifling amount ; but 

 as it was not attached to this plant, and moreover was deprived of the 

 stimulus of light, I imagine that it could not have contributed in the 

 slightest degree to the oxygenating of the water: the two cotyledons, 

 never having put forth leaves, could not have had any influence either. 

 On the other hand, we see many causes that we should have expected 

 would have rendered the water unfit for the maintenance of life, and 

 many sources whence it might naturally have been thought that 

 carbon would have been abundantly generated ; the decomposing 



