THE WONDERS OF A] AX REEF 307 



of a brain. Other species grow in masses, having 

 irregular surfaces with wavy or scalloped borders 

 Agaricias, perhaps; nearer the top are the more 

 delicate branching forms, the madrepores. The 

 color of most of these corals is a rich, warm brown, 

 but the exposed, growing edges are much lighter. 

 Porites, sometimes in masses or developing into 

 heavy club-shaped branches, are common. Then 

 there are the millepores, corals resembling some 

 of the more slender sponges, but growing in large 

 heads. 



The Alcyonarians, which include the sea fans, 

 are everywhere in evidence growing out from the 

 masses of coral and often surmounting them; the 

 most abundant is Gorgonia ftabellum, the ordinary 

 sea fan, either yellow or purple. Almost as num- 

 erous and equally beautiful is Gorgonia acerosa, 

 composed of slender branches instead of the lace- 

 like network of the first. There are two other 

 Gorgonias, one with heavier branches than ace- 

 rosa, and from which the corky substance near 

 the base falls away. All these Alcyonarians are 

 reef dwellers and live only in warm waters. They 

 are each a colony of polyps living upon a central, 

 horny, flexible axis, thus differing from the true 



