120 Natural History of Molluscous Animals, 



centre of this epiphragm (of Helix pomatia) is an exceedingly 

 minute orifice, communicating with an umbilical cord, which 

 is connected with a fine placenta-like tissue of vessels, pene- 

 trating into the pulmonary cavity itself; and this minute ori- 

 fice, although not large enough to admit a drop of water, is 

 of sufficient capacity for the passage of that quantity of oxy- 

 genated air necessary for the purposes of extremely slow, but 

 not totally extinct, respiration. If this orifice be covered 

 over with a coat of wax or varnish, so that all possible con- 

 nection with external air be excluded, animal life becomes 

 altogether extinguished, never to be again restored. We have 

 observed this minute puncture in the winter covering of the 

 H. ericet5rum and some others ; and it is probable that all 

 whose aperture is closed during the cold season only, are fur- 

 nished with this beautiful apparatus for the preservation of 

 life." {Manual of Land and Freshwater Shells, p. 46.) I re- 

 commend you to examine into those very interesting state- 

 ments ; and, if your own observations confirm them, they will 

 materially alter some inferences which have been drawn from 

 Gaspard's experiments, and adopted by us, in reference to 

 the total cessation of the action of the lungs and heart. That 

 snail does not reach this northern latitude; but I have exa- 

 mined, too carelessly however, the epiphragm of Helix aspersa 

 during its hybernation, and always find a small aperture in 

 it ; and also, in the aquatic tribes, I find a larger hole in their 

 thin winter operculum, intended, assuredly, to keep up the 

 communication between the pulmonary cavity and circum- 

 ambient medium in their season of repose. 



There is something admirable in this curious adaptation of 

 the economy of the hybernating creatures to their situations ; 

 for otherwise they could not live beyond a single summer in 

 the countries which they now inhabit with impunity to them- 

 selves. If, during their active state of existence, you were to 

 keep a Limneus, or any other aquatic pulmoniferous species, 

 immersed in water for only one short day, it would die irre- 

 coverably; but it remains under water, perhaps with the 

 surface frozen over, for three or four months uninjured, when 

 the system has been prepared, in autumn, for the change. 

 And so of the land kinds : they perish if deprived of air for a 

 few hours only in summer, or if exposed to an artificial cold 

 not lower than the cold of winter; but in a state of hyberna- 

 tion they respire, if any, such a small quantity of air as is not 

 to be appreciated, and brave our longest and severest frosts 

 without peril and without pain. " O Lord, how glorious are 

 thy works ! thy thoughts are very deep ! " 



Sept, 26. 1833. G. J. 



