Corals. 59 



The family of Corticate Corals are well represented in the Aqua- 

 rium. To begin with we have the Black Coral , Antipathes (Fig. 107), 

 and the Sea-fan, Gorgonia (Fig. 105), possessing skeletons which consist 

 of a horny substance. The branches of Gorgonia all lie in one plane, 

 and when the polypes protrude their bodies and expand their tentacles, 

 they project like small feathery flowers on either side of each branch. 

 In the Bay of Naples there exist white , yellow , and red Sea-fans , the 

 last being the most numerous. Antipathes has a glossy black skeleton, 

 which attains in large specimens the thickness of a finger ; it is used, 

 although rarely, as the so-called black coral for ornamental purposes. The 

 skeleton of the White Coral, Isis (Fig. 104), consists of alternating pie- 

 ces of horny and calcareous matter ; in the Red Coral which belongs to 

 the same family, the skeleton is composed entirely of carbonate of lime 

 or chalk. 



The great value of the Red Coral, Corallium rubrum (Fig. 106), 

 for ornamental purposes is due to its beautiful colour, and the hard texture 

 of its skeleton, enabling it to take a high polish. Te acients valued corals 

 greatly , but they had a wholly erroneous idea of their nature , an idea 

 shared even now by many people; they considered the Coral to be a plant, 

 which remained soft while in the sea, but which became hard suddenly 

 on being taken out of the water. But if a branch bo examined, as soon 

 as it has been fished from the sea , it will be found to be enveloped by 

 a coating, also of red colour, just as the wood of a tree is enveloped by, 

 its bark. Such a branch replaced carefully in a large vessel of fresh sea- 

 water will after a short time show at numerous points of its surface the 

 expanded coral-animals, each with its eight feathery tentacles. Each in- 

 dividual has the structure of a polype, as described above, and is orga- 

 nically connected with all the others by means of canals, which transmit 

 food from one living polype to the other. In the covering besides these 

 canals, are numerous microscopic spindle-shaped particles of carbonate of 

 lime; the axis is formed by a fusion of such particles. This structure of 

 the coral is very readily distinguished under the microscope, by the aid 

 of which instrument all imitations can be easily detected. Corals repro- 

 duce by means of eggs or by buds. There exist separate male and fe- 

 male colonies , besides those which bear both sexes ; sometimes , too, 

 hermaphrodite polypes (individuals with male and female reproductive 

 organs) are found. The egg develops within the maternal polype into a 

 pear-shaped being, which makes its way out through the mouth of the 

 mother-polype and swims about freely for some time; after this it fixes 

 itself with one end and becomes transformed into a polype, which forms 

 new individuals by budding and thus gives rise to a new colony. 



The Red Coral is a gift of the Mediterranean. Here it grows on 

 rocky banks near the coast at a depth of from 40 to 100 fathoms, rarely 

 deeper, and is especially obtained on the Ionian Islands and on the coasts 

 of Algiers and Tunis; the last named place alone yielding about 60,000 

 pounds a year, valued at two million francs. There is also a coral bed 

 between Naples and Capri, and from it the specimens in the Aquarium 

 are obtained. The apparatus for coral-fishing consists of a cross made of 



