GARDEN-SLUG. 193 



but instead of having a simple shell, adhering to that part 

 which is the seat of the breathing cavity, the hinder ex- 

 tremity of the animal is enclosed within a small spiral and 

 fragile shell, covered with a green shining epidermis, into 

 which he can only partially retire. 



One, therefore, of these neglected mollusks carries his 

 spoon-shaped shell externally, about the middle of his back; 

 another, within a fleshy shield upon his neck ; a third bears 

 it attached to his tail ; a fourth presents it as an obvious 

 and shell-like appendage. And yet, although no con- 

 chologist would deem either the one or the other worthy of 

 a place in his cabinet, their construction is equally deserv- 

 ing of regard, as those which are elaborately painted and 

 adorned. 



The mollusks, also, though plainly coloured, and ap- 

 parently of little worth, are beautifully tinted ; every part 

 of even the common slug is varied with light and dark 

 spots, arranged with inimitable skill. 



Look on that feeble creature, and observe how readily he 

 progresses, without feet, a small locomotive engine, and 

 moving occasionally with a considerable degree of swiftness. 

 But how is the want of feet compensated ? By the joint 

 action of longitudinal and annular fibres, which are capable 



o 



