X 



on the first : in general their branches appear directed 

 towards the main sea. 



The larger Polypidoms are rarely found in places 

 exposed to violent currents, or the full shock of the 

 waves. It is in the hollow of rocks, in the submarine 

 grottos, in the shelter of large and solid masses, and 

 above all, in those gulfs where the waters are not 

 agitated, that these singular beings fix themselves. 

 Many of them appear formed to share the powerful 

 action of the surges ; their pliant branches bending to 

 the movements of the waters, and balancing the ani- 

 mals that form them in the agitated medium. Others 

 again, constructing immovable and rocky dwellings, 

 give them the form of tunnels, placing themselves in 

 the interior : while some, by their re-union or aggre- 

 gation, form an extended mass, narrow in proportion 

 to its length, prolonging it uninterruptedly many ter- 

 restrial degrees, and forming an immovable dike, which 

 usually crosses the great currents of the ocean, whilst 

 its solidity and greatness are continually augmenting. 

 Sometimes these madrepore rocks curve in the form 

 of a circle ; the polypi that inhabit it, established in 

 its interior, elevate by slow degrees their rocky dw^ell- 

 ings to the surface of the waters : thus, ever sheltered 

 in their labours, they load by slow degrees the bottom 

 of the deep ; but in the higher part of this impenetrable 



