CORAL 607 



Not only from a scientific but also from an economic standpoint it is important 

 to know the period required by a coral-colony to attain its full growth, but there is much 

 •diversity of opinion upon the point. The length of the period probably varies with the 

 <;onditions under which the colony lives, and more especially with its depth beneath the 

 surface. 



In the opinion of many experts a coral-stock reaches its full size only after a period of 

 thirty years, but others maintain that well-grown stocks are to be found on coral-banks 

 which have been fished very much more recently than thirty years previously. Thus 

 at the beginning of the nineteenth century the fishing of the coi-al-banks on the north 

 ■coast of Africa was abandoned, in consequence of war, for a period of four years, and when 

 fishing was again commenced, an unparalleled amount of coral was harvested, many pieces 

 ■of exceptional size being found. 



Near Vico Equense, in the neighbourhood of Sorrento, in the Bay of Naples, is a coral- 

 bank situated six miles away from the coast, on which the coral, at a depth of 60 feet, is 

 supposed to require eight years to attain its maximum size, while at greater depths it 

 requires still longer. The coral-bank which stretches along the coast of Sicily, from the 

 Point of Faro to a point many miles south of the town of Messina is divided into ten 

 sections, one of which is fished every year. A period of ten years therefore elapses between 

 consecutive fishings of each of these sections, and this is sufficient to admit of the coral- 

 stocks reaching their full size. A rich yield of coral was obtained from a bank still further 

 south, near San Stefano, which had not been fished before within the memory of man. 

 Notwithstanding the fact that the bank had remained undisturbed for centuries, the coral- 

 stocks were no larger, and only about one-third thicker than those known to have developed 

 within a period of ten years. It may be concluded from this that a coral-stock continues 

 for a time to grow in thickness after it has ceased to grow in length. 



The fact that the development of a coral-colony is greatly influenced by the conditions 

 under which it lives is pointed to by the observations of coral-fishers in the Bay of Naples, 

 ■among other regions. The coral formed off the west side of the bay is more beautiful 

 and regularly formed than that obtained off the opposite coast near Sorrento ; a difference 

 which is attributed to the fact that the coast near Sorrento on the east consists of limestone 

 rocks, while the islands of Nisida, Procida, Ischia, &c. on the west are constituted of 

 volcanic tuffs, which are obviously more suitable for corals than the former. 



The discovery of the conditions most favourable for the development of fine coral has 

 been, and is, the subject of much experimental study, but no very valuable result has yet 

 been obtained. 



The polyp, Corallium rubrum, which forms precious coral is placed by systematists in 

 the sub-kingdom Coelenterata, class Anthozoa, sub-class Alcyonaria or Octactinia, all the 

 members of which have eight tentacles and eight mesenteries. 



Precious coral, as we have seen, forms the skeleton of small isolated colonies, but the 

 reef-building corals, by whose industry are reared the coral-reefs and islands (atolls) of the 

 Pacific Ocean and other warm seas, do not differ essentially in their organisation from 

 precious corals, the chief difference being the possession of six mesenteries and of six, or some 

 multiple of six, tentacles. Those corals which agree with the reef-building corals in this 

 respect, constitute the other division of the class Anthozoa, namely the sub-class Zoantharia 

 or Hexactinia. This sub-class comprises three orders of corals : the Madreporaria or stony 

 corals, which includes most of the reef-building corals ; the Actiniaria or sea-anemones, 

 Avhich are destitute of a calcareous skeleton and remarkable for their gorgeous colouring ; 

 and the Antipatharia, including the " black corals," the skeleton of which is homy. 



