166 THE HALL OP SHELLS. 



arborescens) — certainly produce audible sounds. 

 Prof. Grant, who first observed the interesting 

 fact in some specimens of the latter which 

 he was keeping in an aquarium, says of the 

 sounds, that they resemble very much the 

 click of a steel wire on the side of the jar, one 

 stroke only given at a time and repeated at in- 

 tervals of a minute or two. . . . The sound is 

 longest and oftenest repeated when the Tri- 

 tonise are lively and move about, and is not 

 heard when they are cold and without any 

 motion. . . . The sound when in a glass vessel 

 is mellow and distinct . . . and obviously pro- 

 ceeds from the mouth of the animal ; at the 

 instant of stroke we observe the lips suddenly 

 separate as if to allow the water to rush into a 

 small vacuum formed within.' 



" The following instance of affection among 

 snails has been recorded by a naturalist who 

 observed it: 'A pair of Helix pomatia, or Ro- 

 man snails, were put in a garden for safe keep- 

 ing. One of them escaped, but, finding its 

 companion did not follow, it returned in quest 

 of its fellow-prisoner.' " 



