PLATE XXV. 



AGARICIA FRAGILIS Dana. 



Fig. 164. — Transverse section through the stomodpeal region of a polyp with seven pairs oi complete mesenteries 

 anil seven alternating incomplete pairs. The upper part of ttie section, with the transversely shortened 

 mesenteries, is the aspect toward the middle of the colony, the lower is toward the periphery. The 

 septal invaginations are both entocix-lic and exocoelic. No directives are present. X 70. 



AGARICIA AGARICITES (Liniui'us). 



Fi«. 16f). — Vertical section through a freshly extruded larva'. On the right side the stomoda'al ectoderm is in 

 continuity with the mesenterial filament of a mesentery extending the whole length of the larva. 

 Zooxanthell'e are mainly aggregated in the endoderm around. the stomoda-al invagination; a few occur 

 witiiin tlie oral ectoderm. Tlie larval cavity is wholly occupied by a vacuolated tissue; the ectoderm at 

 the aboral extremity is greatly modified from tliat elsewhere, nervous elements being very prominent 

 and gland cells sparse. X 250. 



Fid. 166. — Transverse section through the stomodaeal region of a larva. Four ]iairs of comiilete mesenteries and two 

 incomplete pairs are present, but no endodermal cavity is yet formed. X 'iOO. 



Fig. 167. — Transverse section through the same larva, shortly below the stomodwal region. .\11 tlie six pairs of 

 mesenteries are filamcntiferous, including tlie fifth and sixth pairs, which are throughout free from the 

 stomoda'um. Divisions in tlie vacuolated tissue are feen associated with the mesenteries. X 300. 

 648 



o 



