526 



GASTEROPODA. 



On opening it, it is found to be filled with an infinite number of very 

 thin laminae that adhere to the walls of its cavity by one of their edges, 

 and become joined to each other as if by communicating branches. 

 The excretory duct of this slime-secretor, which, we may observe, is 

 found to exist in many other genera of Gasteropods, accompanies the 

 rectum to its termination, where it opens externally in the immediate 

 vicinity of the orifice leading into the respiratory chamber. 



Fig. 264. 



Anatomy of the Snail (Helix pomatia). 



(1389.) An organ, named by Swammerdam the "sacculus calcareus," 

 has recently been supposed by Mr. Jacobson to perform the office of a 

 kidney. " Chemical analysis of the matter secreted by this viscus has 

 led him to discover in it uric acid, ammonia, or calcareous salt, and 

 water. He was unable to discover any trace of uric acid in any other 



