32 EAMBLES IN SEAECH OF SHELLS. 



paratively small and flat shell, which serves to 

 protect the heart, liver, and other vital organs. In 

 the colour of the hody and size of the shell it 

 varies very much ; hence varieties have come to be 

 described as new species. It is said to be the 

 only land mollusc which has truly predaceous habits, 

 feeding on earthworms, which it pursues under 

 ground, and devouring snails, slugs, and even 

 others of its own species. Dr. Ball writes : "I 

 first became aware o this Testacella preying on 

 worms by putting some of them in spirits, when 

 they disgorged more of these animals than I thought 

 they could possibly have contained ; each worm was 

 cut, but not divided, at regular intervals. I after- 

 wards caught them in the act of swallowing worms 

 four and five times their own length." 



When following the worm through its winding 

 tunnels, the Testacella finds in its small flat shell 

 a useful defence against similar attacks upon itself 

 from the rear, for as it moves along, the shell serves 

 to block up the passage, and at the same time acts 

 as a shield by which the whole body is guarded. 

 In dry weather this slug retires into a sort of nest 

 or cocoon, formed of slime, which gradually dries 



