OKI.KNTKKATA 



73 



edge of the mesenteries, beyond the inner end of the oesophagus, 

 often possesses a greatly twisted thickening, the mesenteric 

 filament, which is very rich in nettle cells and gland cells. In 

 some species there occur, on the edge of the mesentery near the 

 attached end of the animal, long white threads, the acontia, 

 which contain numerous nettle cells, and may be protruded 

 from the mouth or through minute pores in the body wall. 

 These may readily be seen in many sea anemones that have been 



truft, 



oet. f 



g.m 



FlG. 57. Tealia cr.Tssicoriris. Dissected, gon, gonads ; gul, gullet ; l.m, longitudinal 

 muscle; Ip, lappet; mes. 1, mes. 2, mes. 3, primary, secondary, and tertiary mesenteries; 

 tnes. f, mesenteric filaments; tnth, mouth ; ost. 1, est. 2, ostia or openings in mesenteries; 

 />.///, parietal muscle; jr ifph, siphonoglyph ; s.m, sphincter muscle; Aw, transverse muscle. 

 (After Parker and Haswell.) 



somewhat roughly handled. Each mesentery is provided with a 

 strong, longitudinal muscle band, which is attached to one side of 

 it, and there is also near the margin a group of germ-cells which 

 arise from the entoderm ; the sexes are separate as a rule. 



In all the Metazoa that we have considered thus far, wher 

 ever there has been a symmetrical arrangement of the parts 

 of the body, it has been a radical symmetry, i.e. the parts have 

 been arranged radially about a central axis. This is true of 

 the Scyphozoa as well, but the elongated mouth on the polyps 



