166 THE HALL OF 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- 
toniz 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 [/elix 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.’ ” 
