(ECOLOGY. 



177 



early life is parasitic on sturgeons' eggs, the compound 

 Cordylophora,) occurring in canals and in brackish water, 

 and the fresh- water Medusoids (Limnocodium and 

 Limnocnidd). Most of the active swimmers are pelagic, but 

 there are also a few active forms in deep water. Many 

 polyps anchor upon the shells of other animals, which they 

 sometimes mask, and there are most interesting constant 



FIG. 93. Commensalism of sea-anemones and hermit-crab. 



irtnerships between hermit-crabs and sea-anemones, e.g. 



etween Eupagurus prideauxii and Adamsia palliata. 



The hermit-crab is masked by the sea-anemone, and may 

 be protected by its stinging powers; the sea-anemone is 

 carried about by the hermit-crab, and may get crumbs from 

 its abundantly supplied table. This illustrates a mutually 



