48 



CORALS 



spaces and sometimes fusing into solid bars and plates, the 

 substance is called Stereoplasm. 



Galaxea. — The genus Galaxea, widespread on East 

 Indian tropical reefs, is a genus which can be easily identified 

 (Fig. i6). The general form is very variable, as in all the 

 genera of the Astraeidae, but the colony is frequently dome- 

 shaped or hemispherical, sometimes throwing out thick lobes 

 or branches, but never being completely dendritic. 



The calices stand up from the free surface of the coeno- 

 steum as vertical cylindrical columns 5-10 mm. in height. 

 Each calyx is about 5 mm. in diameter, and separated from 



its neighbours by a 



A 



B 



Fig. 



distance of about the 

 same measurement. 



There are twenty- 

 four conspicuous 

 septa, twelve large 

 and twelve small, 

 alternating with one 

 another, and in some 

 calices there may be 

 seen, in addition, 

 twenty - four minute 

 septa between the 



15.— Diagrams to illustrate the three mOrC COnspicUOUS 

 principal kinds of endotheca. A, tabulae; B, QT->pc TVip sfnta are 

 dissepiments ; C, stereoplasm. ' ^ 



exsert, that is to say 

 thev project upwards, above the lip of the calyx wall. There 

 is no true columella, but the larger septa are connected at 

 the base of the cup by dissepimental bars or trabeculae. 

 There are no pali. The surface of the septa is rough, but 

 is not armed with spines. 



The common coenosteum lying between the bases of the 

 calices, which in this case is called the " Peritheca," is 

 marked bv a number of small blister-like swellings, and is 

 therefore technically called " Vesiculate." 



In certain parts of the colony where growth is active, 

 such as the free edges or the ends of the lobes, a number of 

 small calices can be seen. These small calices have been 



