16 LIVEEPOOL BIOLOGICAL SOCIETY. 



glass jar of fresh water. In this they remained day after 

 day with the opercuhim or hd which closes the mouth of 

 the shell tightly shut. At the end of the second day, I 

 took one of the specimens out of the water, and on opening 

 the shell found that the animal was alive and active inside. 

 On the fourth day two specimens died, on the sixth day 

 four more, and by the end of the eighth day all of them 

 were dead. Whether this death was due merely to the 

 prolonged immersion in the fresh water, or may have 

 been caused by the water becoming slightly impure, was 

 uncertain, so the experiment has been repeated several 

 times since (see below, jar B). 



It is easy to tell whether the Littorinas are alive or 

 dead, as, so long as a specimen is alive, it remains 

 tightly shut up in its shell, while whenever it dies the 

 operculum opens and a part of the "foot" of the animal 

 protrudes in the form of a white mass, which rapidly 

 begins to decompose. 



I next collected from the rocks a fresh set of specimens, 

 which were placed as follows : — 



(A) Ten specimens in a jar of clear sea -water, under 

 muslin (see below, fig. 3). 



(B) Ten specimens in a jar of fresh water. 



(C) Ten specimens in an empty dry jar {i.e. in air). 



(D) Twenty specimens in a slate and glass aquarium, 

 half full of sea- water and open at the top. 



The jar A (see fig. 3) was so arranged as to have a piece 

 of coarse muslin {m) spread over a hoop just below the 

 surface of the sea- water, the object being to allow the air 

 to have free access while preventing the molluscs from 

 coming to the surface of the water. 



These four sets of specimens were examined every twelve 

 hours for three days, and their positions and apparent 



