1U 



COELEXTERATA. 



The nervous system has the form of a plexus of multipolar 

 ganglion cells placed between the muscle-fibres and the ectoderm 

 cells. In addition to this peripheral plexus there are special 



FIG. 101. Cnrmarina (Geryonia) hastata (from Chun, after Haeckel) a sex-radiate Tracho- 

 medusan. s.u sub-umbrella; a manubrium ; v velum; n nerve-ring; rv circular vessel; 

 en thickened tract of ectoderm at edge of bell ; t marginal tentacle ; mu interradial longitu- 

 dinal muscular bands of the manubrium ; o mouth ; g stomach ; cr one of the six radial 

 canals ; ov ovaries on the sub-umbrella-wall of the radial vessels ; c.cp centripetal, blindly 

 ending radial vessel ; pe peronium. The teutaculocysts are shown near the base of and 

 between the tentacles. 



