PLATE XXV. 



AliARICIA FBAGILIS Dana. 



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

 and seven alternating incomplete pairs. The upper part of the 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 entocoelic and exoceelic. No directives are present. X 70. 



AGARICIA AGARICITES (Linnaeus). 



Fig. 165. — Vertical section through a freshly extruded larvae. < >n the right side the stomodaeal ectoderm is in 

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

 Zooxanthelhe are mainly aggregated in the endoderm around the stomodaeal invagination; a few occur 

 within the oral ectoderm. The larval cavity is wholly occupied by a vacuolated tissue; the ectoderm at 

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

 and gland cells sparse. X -50. 



Fig. 166. — Transverse section through the stomoda-al region of a larva. Four pairs of complete mesenteries and two 

 incomplete pairs are present, but iui endodermal cavity is yet formed. X 300. 



Fig. 167. — Transverse section through the same larva, shortly below the stomodaeal region. All the six pairs of 

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

 stomodseum. Divisions in the vacuolated tissue are seen associated with the mesenteries. X 300. 

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