80 IXVEKTKBliATE AXIMALS; 



belonging tn the iiidixidiKil zouitls, without any common calcareous 

 baiis secivtcil by a cit'nosai'c. 



Aa bi'foi'o a.iiil, Iht; "septa" are verticil partitions, which divide 



Fi^. 00. — A conipouiid Coral(Astr(rOj i-ialUda) in its lining state. (Attei- Dana.) 



the space contained within the walls (the so-called "thcca") of the 

 coral into a scries of coiniiartments. The septa spring from the 

 inner snrf.-icc of tlie "Ihtca" (fig. 51), and advance towards its 



rig. fA. — .\, Tran,s\prsp sfrtion of a simple selprnileriiiic coral, showing how Itie 

 sjiaee iiii'liKiei] within llie wall or "llicpa" is siiliiliviiletl by the railiatiiig se]ita, 

 llii- crjilri' hriiig niTii[af(t hy llii- enl iinn'lla ; R, Tratisveise .seetion of a slniiile 

 l!n-oso enial, shnwiii;; tlie wall aiM (he r.eliatilig selita. 



■ ■'iilro. ( )fton llic Hrpta unite centrally willi a calcareous jiillar or 

 V »\, Cio " .•ol;niic'll;i, " ; and (lii'y :irc (.f ddi'ei-ent breadths. A certjiin 

 n n]]|ji r .if thi;ni c.\teiid (jintc to llic ccnti'e of the coral, where they 



