84 



ANTHOZOA. ZOANTHARIA 



septum, and as growth proceeds these become more widely 

 separated from the cardinal septum, and eventually form 

 the alar septa of the adult (fig. 34 c) ; afterwards, two 

 septa (3) are added, one on each side of the counter septum, 

 and these also spread outwards as growth proceeds (as 

 indicated by the arrows in fig. 29 D). The six septa now 

 present are regarded as the primary septa (1, 2, 3). The later 



® 



C 3, -3 



b l b 



Fig. 29. Development of the septa in a simple Eugose Coral, Zaphrentis. 

 1 — 3, primary septa; 1, cardinal septum; 1' counter septum; 2, alar 

 septa; 3, counter-lateral septa; a, b, c, later septa (metasepta). 

 (After Carruthers.) 



septa (sometimes termed metasepta) are introduced in pairs ; 

 these appear at four points — one septum on each side of the 

 cardinal septum (1), and one between each alar septum (2) 

 and the primary septum (3). The two pairs which are first 

 added (fig. 29 E, a) are attached to the cardinal sides of the 

 primary septa 2 and 3 ; similarly later pairs (fig. 29 F, G, b, c) 



