246 THE INHABITANTS OF THE SEA. 



their juices with a bloodthirsty proboscis. Some (Argulus, 

 Caligus) wander about freely on the body of their victims as 

 grazing animals on their pasture grounds, or even make ex- 

 cursions in the water, where they will turn over and over several 

 times in succession like mountebanks ; others (Lerneaej, after 

 having, like the barnacles, indulged in a vagabond existence in 

 their first youth, remain ever after clinging to the spot on which 

 they originally settled, and where their body undergoes such 

 remarkable transformations that not a vestige of the crustacean 

 structure which characterised their erratic life remains. 



As we continue to proceed from the lower to the higher forms, 

 we find, on the next stage of crustacean life, the numerous 

 families of the Entomostraca ; some bristly-footed (Lophyropoda), 

 withasmallnumberof legs and with respiratory organs attached to 

 the parts in the neighbourhood of the mouth, others gill-footed 

 (Branchiopoda), with numerous foliaceous legs, serving both for 

 respiration and swimming. Some of these creatures, which are 

 generally of such minute size as to be only just visible to the 

 naked eye, have an unprotected body (Branchipus), but gene- 

 rally they are enclosed within a horny or shelly 

 casing, which sometimes closely resembles a 

 bivalve shell in shape and in the mode of junction 

 of its parts, whilst in other instances it forms a 

 kind of buckler, an opening being left behind, 

 through which the members project. 



Though enjoying a royal title, the King-crabs, 

 or Limuli, occupy in reality but a low rank 

 among the crustaceans, and are hardly superior in 

 Eing-Crab. organisation to the Entomostraca. They are of 

 large size, sometimes attaining the length of 

 two feet, and of a very singular structure, the bases of the legs 

 performing the part of jaws. The best-known species comes from 

 the Moluccas, where they are often seen slowly 

 swimming in the sheltered bays, or still more 

 slowly crawling along upon the sandy shores. 

 In the Edriophthalmia are included the lower 

 sandhopper. crustaceans that have no carapace, and whose 

 thorax and abdomen are distinctly composed of articulated 

 segments. The numerous legs are variously formed in the diffe- 

 rent genera for springing, walking, or swimming ; and respira- 



