i68 



CORALS 



arranged in rows (Fig. 80), and the student of zoology will 

 recognise a close similarity between these zooecia and those 

 of the common sea-mat, Flustra. One of the most important 

 differences between Lepralia and Flustra is that, w^hcreas 

 in the former the walls of the zooecia are impregnated with 

 calcareous matter, in the latter they remain horny in 

 texture. From this difference it follows that in Lepralia 

 the fronds are rigid and brittle, whereas in Flustra they 

 are flexible and tough. 



Cellepora. — The genus Cellepora includes some species 

 which form, in tropical waters, large spherical, oval, or 



irregularly shaped masses 

 of coral substance (Fig. 

 81); but as the walls of 

 the zooecia are relatively 

 thin the texture of these 

 masses might be called 

 spongy, and they feel light 

 in the hand as compared 

 with other corals. 



In these tropical species 

 the lumps of Cellepora 

 are frequently invaded 

 by other organisms which 

 seem to live and thrive 

 without material incon- 

 venience to their host. 

 In one ramified specimen from shallow water off the Aru 

 Islands the surface is perforated by little round holes, 

 situated at approximately equal distances apart, in which 

 were Uving sea anemones. In other specimens barnacles 

 and worm tubes are found. 



When these lumps of Cellepora are cut across it is generally 

 found that there is a core or kernel of some foreign substance, 

 such as a stone, another coral, or a branching Gorgonian, upon 

 which the Polyzoon has built up layer upon layer of zooecia 

 until the original support is entirely submerged. The final 

 shape of the lump is due in large measure to the shape of the 

 foreign substance on which it started to form its colony. 



Fig 



80. — Lepralia fuliacia. 

 of a part of a colony. 



Surface view 

 16 diams. 



