CHAPTER III 



CRUSTACEANS 



NO branch of the animal kingdom is more abundantly- 

 represented on land or in the waters — fresh, 

 brackish and salt, than is that of the jointed animals 

 or Arthropoda. The group includes the Crustaceans, 

 Trilobites, Spiders, Centipedes and Insects, all of which 

 have representatives within the maritime zone, the 

 Crustaceans being, however, predominant in that region. 

 The Crustaceans are known to the general public by 

 such common forms as the Wood Louse, Sandhoppers, 

 Barnacles, Shrimps, Crabs and Lobsters, animals sufficiently 

 diverse in appearance and economy yet all presenting certain 

 points in common. The bodies of all these creatures are 

 divided into segments, each segment bearing a pair of 

 appendages. These organs are modified in a variety of 

 ways, some serving as tactile organs, others being employed 

 for seeing, chewing food, or various means of progression. 

 The animals are encased in more or less unyielding suits 

 of armour which must be periodically cast off to permit 

 of expansion, a new shell being formed beneath the old 

 one. Reproduction is almost invariably effected by means 

 of eggs, the young sometimes resembling the parents, but 

 in many cases passing through a series of complex trans- 

 formations before reaching the adult form. 



33 c 



