674 



THE SEA-FAN. 



BKAIN-COKAL. Astrtea pallida. (One-half naiural size.) 



In the accompanying illustration is seen a figure of that remarkable coral which is 

 popularly called BRAIN-STONE, or BUAIN-CORAL, because the convolutions into which the 



corallum is moulded much resemble those of 

 the human brain. 



The animals of this genus are always 

 united together in long waved series, each 

 having a distinct mouth and series of very 

 short tentacles. T3ie cells are very shallow, 

 and the valleys formed by their union are 

 separated from each other by distinct ridges. 

 The shape of this coral alters greatly with 

 age, somewhat resembling the top-shells when 

 young, but becoming rounded above when 

 adult. The Brain-coral is found in several 

 of the hot seas. 



Among the Asteriadae, as these creatures are called, in consequence of the star-like 

 appearance of the polype or animal, the ORGAN-PIPE-CORAL, is perhaps the most striking. It 

 forms, as far as is yet known, the only example of the group to which it belongs, and which is 

 called Tubuliporina, on account of the multiplied series of regular tubes from which it is 

 formed. As will be seen by reference to our engraving, in this beautiful coral the tubes are 

 arranged like the pipes of a church-organ, or the storied rows of basaltic columns of the 

 Giant Causeway. 



The color, too, is very pleasing, being a delicate pink, so that even the empty and lifeless 

 corallum forms a really beautiful object. When living, however, it may fairly lay claim to 

 the title of magnificent, for each tube is clothed, formed, and vivified by a light green polype, 

 whose color contrasts beautifully with that of the structure which is raised by that soft and 

 feeble body. 



Two other species of true coral, such as are used so largely in the manufacture of orna- 

 ments, are termed Corallium fecundum, and Corallium nobile. 



These beautiful zoophytes seem to be found only in the Mediterranean, where regular 

 fisheries are established and the corals 

 dragged from their recesses. The appli- 

 ances, however, are very rude; and it 

 is likely that more elaborate machinery 

 would reap a rich harvest by permitting 

 some selection to be made and by ena- 

 bling the fishers to regulate the dimen- 

 sions of the groups of coral branches. 

 Although the stony centre is so thick 

 and solid, the substance of the animal 

 is quite delicate and membranous, en- 

 veloping the corallum like wetted gold- 

 beater's skin. 



A fan-like object is popularly called 

 from its shape, the SEA-FAN (Gorgbnia 

 flabellurri), and well deserves that title. 

 In this genus the branching arms are 

 united by a number of transparent 

 pieces, which are, in fact, developments 



of the branches, are covered in a similar manner by the investing membrane, and bear the 

 living polypes on their surface. The whole structure easily dries, and may be found in most 

 curiosity shops, or in the dwelling-houses of mariners, who have brought home these remark- 

 able objects as presents to their wives. 



The Gorgonias, Sea-fans, Sea-feathers, Sea-whips, etc., belong to the Order Halcyonoida 



ORGAN-PIPE CORAL. TuHpara tptinga. (Natural size.) 



