ANTIPATHARIAN CORALS 141 



ZOANTHIDEAN CORALS 



Gerardia savalia is the accepted name for a remarkable 

 Mediterranean black coral which was first mentioned by 

 Ferrante Imperato in 1599 under the name Savaglia. 



From the fact that it has a black horny axis it was, until 

 recent times, classified with the Antipatharia, but the 

 researches of Carlgren ^ have shown that the polyps which 

 form the axis of Gerardia have a different structure from the 

 Antipatharian polyps, and resemble in essential characters 

 those of another group of Coelenterata called the Zoanthidea. 

 It is not necessary to give full details of the structure of these 

 polyps, but it may be said that they have a great many 

 more tentacles (twenty-four or more) and mesenteries than 

 the polyps of the Antipatharia, and that when retracted 

 they form a thicker bark or crust over the axis. 



The colony is said to begin life by encrusting a stem of 

 a Gorgonia, but soon surpassing its support in growth it 

 forms a basal horny skeleton of its own and builds up very 

 large branching colonies. 



Many authors refer to the great size which specimens of 

 this coral reach, and it is possible that Gerardia was the 

 principal source of the black coral that was used by the 

 Mediterranean races in early times. 



A specimen, now in the British Museum, that was 

 dredged up from a depth of 20 fathoms of water off the 

 Grecian island of Negropont, is 6| feet in height and has 

 an expanse of 6 feet 8 inches. The main trunk from 

 which the branches arise is i foot 5 inches in circumference.^ 



The anatomy of Gerardia was first described by de Lacaze- 

 Duthiers,^ who gave some beautiful illustrations of the 

 anemone-like polyps when fully expanded. The colour of 

 the polyps is said to be normally a greenish-yellow, but at 

 the time when they are charged with reproductive bodies 

 this colour, as well as the usual transparency of the tissues, 

 may be obscured by the brick-red eggs or the white testes. 



1 Carlgren, Ofvers K. vet. Akad., 1895, 5. 



- F. J. Bell, Trans. Zool. Soc, London, 1891, p. 87. 



^ De Lacaze-Duthiers, Ann. Sci. Nat. (5), ii., 1861, p. 169. 



