38 THE SEA-ANEMONE 



(g) The acontia, long delicate threads springing from the edges of the 

 mesenteries ; they bear nematocysts, and can be protruded through 

 minute apertures in the body- wall known as cinclides. 

 (h) The genital organs or gonads on the primary mesenteries. 

 (i) The muscles of the mesenteries. These are : 



(i) The longitudinal or retractor muscle, a narrow band stretching 



from the base to the disc on one side of each mesentery, 

 (ii) The parietal muscle, passing obliquely across the lower angle of 

 the mesentery. 

 (j) There is a circular sphincter muscle around the oral margin. 



Genital organ 



Mesenteric 

 filament — 



Basal disc 



Fig. 13. — A. Longitudinal Section of a Sea-anemone (at the position indicated by the arrow in 

 Fig. 12, B.) ; B. Longitudinal Section (diagrammatic) of a Sea-anemone. 



