186 THE HARMONIES OF NATURE. 



In this wonderful instance of animal instinct, one knows not 

 what is most to be admired the beautiful adaptation of the 

 animal's structure to its peculiar mode of life, or its almost 

 incredible ingenuity. 



The crustaceans have various modes of escaping the attacks 

 of an over-powerful enemy. Some, like the shrimp or the lob- 

 ster, bound rapidly through the waters ; others, as we have seen, 

 are excellent runners on the land. Many form deep burrows, 

 into which they retire at the first alarm ; others hide themselves 

 quickly under boulders or tufts of algae, to avoid a disagreeable 

 meeting with a voracious fish or hungry kinsman. Some feign 

 death, contracting their claws, and allowing themselves to be 

 thrown about like inert bodies ; others, like the small pea-crab, 

 claim the hospitality of large bivalve shells, as a substitute for 

 the softness of their own integuments. In this safe retreat 

 they live upon the minute animals which their involuntary 

 protector engulphs on opening his folding-doors ; for it is of 

 course but a poetical fiction that a friendly connection exists 

 between them that the mussel is warned of the approach of in- 

 quisitive cuttlefishes, or prying sea-stars, by a gentle pinch of 

 his little lodger and that the latter, when after an excursion he 

 finds the premises closed, has only to knock to be again ad- 

 mitted ! 



Another large family of crabs is likewise indebted for 

 a dwelling to another and a lower class of animals. The 

 hermit-crabs or paguri have, indeed, the forepart of their 

 body armed with stout claws and covered with a shield, 

 but terminate in a long, soft, and utterly defenceless tail. This 

 cumbersome and exposed hind-part is not formed for swim- 

 ming, and its weight prevents them from running, so that 

 nothing remains for the poor creatures but to look about them 

 for some shelter ; and this is afforded by several conchi- 

 form shells buccina, neritse in which they take up their 

 abode, attaching themselves to their interior by a sucker with 

 which the tail is furnished at its extremity, and also holding by 

 the six false legs which they bear at their hinder portion. 

 When they are feeding or walking, the head and thorax project 

 beyond the mouth of the shell ; but when they are alarmed they 

 draw themselves in, closing the mouth with one of the claws, 

 which is much larger than the other, and fits the opening of 



