18 LIVERPOOL BIOLOGICAL SOCIETY. 



observation for some time longer; the molluscs only began 

 to die on the thirteenth day — a marked contrast to jar A. 

 Consequently these ''marine" molluscs can live longer in 

 fresh water than in sea-water. 



In C some of the specimens remained, in the contracted 

 state, where they were put ; while others crawled slowly 

 about on the sides of the jar, a piece of glass over the 

 top prevented their escape. None died : apparently, then, 

 they can live best in the air. 



Of the twenty specimens in the aquarium (D) seven had 

 crawled out of the water in fifteen minutes; at the end of 

 twelve hours fifteen had crept up the slate sides out of the 

 water, and at the end of twenty-four hours nineteen had 

 emerged from the water, and had travelled to distances of 

 from one to four feet from the aquarium over the stone 

 floor and painted plaster walls of the laboratory. I 

 marked pencil rings round the five which had crawled 

 farthest at the end of the second day, and found they went 

 no farther after that during the two months they were 

 under observation. 



This experiment has been repeated several times with 

 the same general result. All the specimens of Littorina 

 rudis put in a contracted state into an open aquarium 

 become active, and in the course of a day or two find 

 cheir way out of the water, and after crawling for a little 

 distance come to rest and remain there indefinitely. I 

 have not noticed any specimens crawling downwards again 

 into the water, even after being for days in the air. 



Next, I made some observations on the specimens at 

 the shore under their natural conditions. The rocks at 

 Puffin Island are reefs and masses of carboniferous 

 limestone, broken up by the waves and worn into crevices 

 and crannies of all sizes and shapes. The Littormas 

 above high-water mark on these rocks are, I find, almost 



