62 CORALS 



or spiny costae. The most usual method of asexual repro- 

 duction is by lateral columnar gemmation, but a process, 

 called fissiparous gemmation by Duerden, also, but rarely, 

 occurs. 



The expanded polyps are light brown in ccjlour, and are 

 provided with twenty-four to thirty-six slightly knobbed 

 tentacles arranged in three or four cycles. The margin of 

 the disc has sometimes a bright iridescent colour. As with 

 nearly all the gemmiparous Astraeids, the polj'ps of Clado- 

 cora are provided with two pairs of directive mesenteries. 



The genera of Astraeidae that do not form colonies 

 {Astraeidae simplices) are among the rarities of museum 

 collections, and our knowledge of their anatomy is very 

 imperfect. 



The essential difference between a simple Turbinoliid 

 coral and a simple Astraeid is that in the latter the base of 

 the cup is more or less blocked by endotheca. 



But some of them differ from the ordinary Turbinoliids, 

 and resemble some of the Astraeids in having the septa 

 armed with numerous spines. Any differences which may 

 exist in the structure of the polyps have yet to be discovered, 

 and it may possibly be proved that the separation of the 

 two groups is unnatural. The solitary Astraeids do not 

 seem to be abundant anywhere in modern times ; a solitary 

 specimen here or a half-dozen specimens there is the onl\- 

 booty of the fortunate collector. In no locality, so far dis- 

 covered, are they found in great numbers. They are not 

 confined to any one region, but may be found in deep or 

 in shallow water in the warmer seas of the world. 



t^AMILY 4. FUXGIIDAE 



The characteristic feature of this familv is that the 

 septa are united by synapticula. The synapticula are bars 

 of solid coral substance that pass horizontally from one 

 septum to another and in doing so perforate the mesenteries. 

 In some respects the Fungiidae are intermediate between 

 the imperforate corals previously described and the perforate 

 corals, for, although the septa and the theca are usuallv 



