ARTHROPODS. CLASS CRUSTACEA 



97 



is open along one side, and allows the feather-like feet to 

 project and produce currents in the surrounding water 

 which brings food within reach. In the acorn-barnacles 

 (Fig. 55) the stalk is absent, and the body, though possess- 



FIG. 55. Barnacles. Acorn-barnacles chiefly in lower part of figure ; goose-barnacles 

 above. Natural size. 



ing the same general character as the goose-barnacles, is 

 shorter, and enclosed in a strong palisade consisting of six 

 calcareous plates. 



The larger number of barnacles attach themselves to 

 the supports of wharves, the hulls of ships, floating tim- 

 bers, the rocks from the shore-line down to considerable 

 depth, and a few species occur on the skin of sharks and 

 whales. On the other hand, there are severaLspecies which 

 are parasitic, and in accordance with this mode of life ex- 

 hibit various degrees of degeneration. In the most extreme 



