62 POPULAR HISTORY OF THE AQUARIUM. 



is flesliY, including the central stem ; but througli the centre 

 of the' latter runs a calcareous column, which serves to 

 strengthen and support the whole. This forms the rudi- 

 ment of a true Coral, and constitutes a bond of union be- 

 tween the Sea- leather and the Asteroid whicli forms that 

 beautiful Coralline known in commerce as the "Precious 

 Coral/' of which red ornaments are made. 



Cock's-Comb, Sea -Pen, Sea-Feather, are the names by 

 which the Pennahda is known ; the former, on account of 

 the colour and general appearance of the upper pinnjc ; the 

 latter, because of the resemblance which every one must see 

 on glancing at the object. 



Pemiatida pliospliorea is unattached : it does not grow 

 fixed to any object, like Gorgonias, etc., but is planted in 

 mud, with its pinnae exposed. And now comes tlie ques- 

 tion, whether it is capable of moving from place to place 

 through its bed, or of raising its body and swimming through 

 the water. Some naturalists have held that it is capable of 

 both motions ; others say that it cannot move voluntarily at 

 all. Its general habits certainly appear to be very stationary ; 

 and we have no direct evidence, derived from actual observa- 

 tion, that the animal is provided with locomotive power or 

 instinct. Yet some authors assert that it swims about freely 



