XYl 



Some commence ami fiiiisli tlieir existence ii»the short 

 space of a day, perhaps an hour, while others live 

 through centuries. The same occurs among the Poly- 

 pidoms ; some have only an ephemeral life, while the 

 existence of others seems eternal. I here speak of the 

 Polypidoms, not of the polypi ; the latter, separately 

 considered, do not appear to have a long life, but on 

 the contrary many circumstances induce us to pre- 

 sume it is very short. 



In the Flustreas, Cellarias and Sertularias are found 

 annual species, and others whose duration is sub- 

 ordinate to the marine plants that support them. In 

 almost all Polypidoms, the lower parts are wholly 

 devoid of animalcula, and in the greater they are only 

 seen at the extremities : some there are, that are en- 

 tirely covered with polypi through the summer and 

 autumn, but they perish with the cold of winter. No 

 sooner however has the sun resumed his revivifying 

 influence than new animals are developed, aud fresh 

 branches are produced upon the old ones ; the lower 

 part appears inert, and deprived of all kind of life ; the 

 Flustreas, Sertularias, and Gorgonias afford us many 

 examples. Arrived at this last stage of existence, 

 the Polypidom languishes, it has no longer the power 

 to resist the destructive influence of time, or the at- 

 tack of those enemies which the energies of life had 

 till then repulsed : some of them feed on its fleshy en- 



