HALF AN HOUR WITH SEA-WORMS. 83 



an ordinary garden cucumber, with the stalk at- 

 tached. This stalk-like portion is protruded and 

 withdrawn at the animal's pleasure, the tip expand- 

 ing and throwing out a series of white thread-like 

 tentacles. One species inhabits deserted univalves, 

 like the Nereis, and seems especially partial to that 

 of the periwinkle. It has a trick, when properly 

 housed, of cementing a wall of sand across the mouth 

 of the shell, leaving a small orifice through which it 

 can protrude its curious trunk and obtain its food. 

 In all these variations in animal structure, the 

 devout mind cannot fail to trace the perfect accord- 

 ance maintained between them and the equally 

 striking variations in the physical circumstances of 

 their habitats. This harmony, like a silver thread, 

 runs through and connects the entire range of the 

 animal kingdom. 



