Chapter VII Crustaceans 



BOTH as regards number of species and 

 individuals the Crustacea exceed most 

 other groups of animal life. A lobster 

 and a wood-louse have little in common 

 at first glance, yet these two creatures, 

 like all the members of the order to which 

 they belong, are built upon much the 

 same plan. In all crustaceans the body 

 is divided into segments, each bearing a 

 pair of limbs which may serve such a 

 variety of purposes as walking, swim- 

 ming, fighting, feeding and digging the 

 home burrow. A few crustaceans are 

 terrestrial, but even amongst these their 

 infancy with a few exceptions is spent 

 in the water. The great majority are 

 aquatic, " peopling " every pond and 

 stream with unseen millions, the forms 



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