SPONGES. 29 



be removed without lacerating or injuring their sub- 

 stance. Although they thrive best in the sheltered 

 cavities of rocks, they come to maturity in situations 

 exposed to the unbroken fury of the surge ; but in 

 the latter situations Dr. Grant observes that they 

 are smaller, and firmer in their texture, like those 

 inhabiting colder climates, and this whether their 

 exposure be to the north or south. They cover the 

 naked sides of cliffs and boulders ; they line with a 

 variegated and downy fleece the walls of submarine 

 caves, or hang in living stalactites from their roofs. 

 In fact, they attach themselves indiscriminately to 

 bodies belonging to the mineral, vegetable, and animal 

 kingdoms, and the individual species seem to have no 

 law with regard to the particular substances to which 

 they adhere. 



The branched Sponges are usually to be met with 

 hanging perpendicularly from the under and shel- 

 tered surface of solid overhanging cliffs, or tabular 

 masses of rock. The flat, spreading species with pro- 

 jecting papillae are generally found on the sides of 

 boulders; while flat specimens, without prominent 

 papillae, are more frequently seen on the under sur- 

 faces of stones, or else enveloping bodies which admit 

 of a little motion by the agitation of the sea. 



The delicate and beautiful Spongia compressa is 

 sometimes found hanging from the surface of Ascidiae, 

 or of flat sponges, as likewise from the rock itself. 

 The Spongia coalita is a branched species capable of 

 rising erect, owing to the great breadth of its base, 

 the firmness of its skeleton, and the frequent anasto- 

 moses of its branches. 



