perfect shells, because they are so fragile that they will break at the 

 slightest touch. Much care is necessary to obtain unbroken specimens. 

 The order to which the bubble shells belong, the Tectibranchiata, 

 comprises several hundred mollusks whose shells are similar in form to 

 the bubble shells. Some are large and others are very small, some thick 

 and solid, while others are thin as paper. The color is generally whitish, 

 but in some species it is greenish, brownish, reddish, or banded with red 

 and white like the ship's-flag bubble shell, Aplustrum. In the boatman 

 bubble shell (Scaphander] the calcareous gizzard is a third as large 

 as the entire shell, the tooth shell, Dentalium entails, being its prin- 

 cipal food. Not all of the mollusks of this order have shells. The 

 sea hares (Aplysia) have large, flabby bodies in which is lodged a small, 

 oblong, transparent shell. This animal lives among the seaweed, feeding 

 upon the vegetation as well as upon mollusks and other animals. It 

 discharges a violet liquid when handled, which caused the ancients 

 to believe that it was poisonous. The old Greek philosophers wrote 

 a great deal on this subject, believing that to even touch the animal 

 with a stick would cause death. Though repulsive looking creatures, 

 they are perfectly harmless, and are even eaten by the natives of the 

 Friendly and the Society Islands. 



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