70 POPULAR HISTORY OF THE AQUARIUM. 



for what is known of their singular structure. Both in the 

 fresh and dried state they are of much greater specific gra- 

 vity than the Sponges, and frequently emit a disagreeable 

 odour. They vary much in form, some being in a shape- 

 less form or crust, and others lobed, fingered, branched, or 

 with rounded mushroom projections. The interior sub- 

 stance is spongy or corky, surrounded by tube-like rays 

 enclosed in a leathery sort of membrane. The tentacles or 

 arms of the animal inhabitants of these productions are eight 

 or more. The cells in which the animals lodge are round, 

 unequal in diameter, and about a sixth of an inch in depth. 

 ^^The AlcyonecE are found in all seas and at various 

 depths, subsisting, it would appear, on marine plants ; they 

 do not however seem to like places which are often left dry 

 by the ebbing of the tide, and hence we have never met 

 with them recent, except about the low-water mark of spring 

 tides, and they seem to dehght in places sheltered by rocks 

 from the sweep of currents or the agitation of the waves, 

 and where the light is rather obscure. They are found 

 therefore to be more numerous in deep w^ater." 



Alcyonium digitatum. 

 The Alcyon, or Kingfisher, — fabled to have formed its nest 



