82 The Under-Water World 



which are directly connected with the 

 creature's brain. These are supposed to 

 transmit and pick up the vibrating 

 messages in .the surrounding water. 



One other British crustacean produces 

 loud sounds under water. This is 

 the little ruby-tinted " snap " lobster 

 (Alpheus rubra), common on the south- 

 western coast in deep water. The 

 " finger " of the big claw of the creature 

 works on a trigger principle and snaps 

 with sufficient force to be audible at a 

 distance of several yards. 



Amongst the most entertaining in- 

 habitants of the under-water world are 

 those hermit crabs who spend the greater 

 part of their lives in one long struggle to 

 cope with the housing problem. The 

 true hermits have the abdomen free but 

 devoid of armour, and to remedy this 

 defect they hide in empty shells or 

 beneath the shelter of sea anemones. 

 The size of a hermit is dictated by the 



