87 



teries (six pairs in Actinia and Peachia), and besides these 

 there may be secondary and tertiary mesenteries which are 

 shorter and do not join the gullet (Actinia has both, Peachia 

 has secondaries only). 



The gullet has usually two siphonoglyphs (Peachia has 

 one). The pair of primary mesenteries opposite each siphono- 

 glyph are directive, and the muscles are on their outer 

 surfaces, not facing. The other mesenteries have the 

 muscles facing, on their inner surfaces. 



Primary and Directive Mesenteries. 



Ectoderm 

 Mesogloea 



Endoderm 



Intra- 

 Septal 

 Cavity 



Siphonoglyph 



FIG. 20. Transverse Section of a Sea-Anemone. 



The mesenteries often have special stinging threads 

 (acontia) which are protruded through openings in the 

 body- wall. (Peachia is without acontia.) 



There is a circular sphincter muscle around the oral 

 margin, and by its constricting action the oral region can 

 be completely closed in. There are no sense organs. 



