8o 



CORALS 



In his description of the species Dcndroplivllin Willeyi, 

 on the reefs of the Cocos Islands, Dr. Wood-Jones says that 

 " when the colony consists of one or two polyps it is coloured 

 bright chrome yellow, w'hen older it is bright vermilion, 

 but at all times it has an iridescence resembling solutions 

 of eosin." 



AsTROiDES. — Another Eupsammiid coral that has become 

 familiar to us is the Astroides calicidaris of the Mediterranean 

 Sea (Fig. ^^). This is the coral to which Boccone gave the 

 poetic name " la pierre etoilee." It usually forms small 



encrusting colonies composed 

 of a number of calices about 

 7-8 mm. in diameter and 4 mm. 

 in height separated from one 

 another by a sparse coeno- 

 steum . The cavity of the calyx 

 is wide and deep, and rising 

 from the centre there is a well- 

 developed conical trabecular 

 columella. The septa of a 

 full - grown calyx are forty- 

 eight in number and arranged 

 in four cycles. There is less 

 regular and complete conflu- 

 ence of the third and fourth cycles of septa in Astroides 

 than is usual in the genera of this familv, but some con- 

 fluence does occur in nearly all the calices. 



The polyps have a bright orange colour, and when fulh- 

 expanded stand up from the calices as tall columns termin- 

 ating in an oral disc surrounded by a crown of forty-eight 

 simple digitate tentacles. 



This coral is of special interest to students of coral 

 morphology, as it was the subject of the important re- 

 searches of de Lacaze-Duthiers and von Koch which laid 

 the foundations of our knowledge of the embryology and the 

 development of the skeletal structures in the Madrepora.ria. 



I'"iG. 33. — Astroides calicidaris. Medi- 

 terranean Sea. J nat. size. 



