21:; 



CCELEXTERATA 



All other important organs arise from the ectoderm. Gonads arise 

 in many species (Lig. 170 from tlic ectoderm of the manubrium; in others 



Fir,, 175. — Rliiipiihiiirma -rrhilur,!. c. rin;; r;innl; c. oxumbrcUa: i:, gonads; /;, oto 

 cysts; }u. stomach; 11, ncrw riii^-, 0, moulli; ,v, subuinln-cUa; 1", :", tciUaclcs of first and 

 second order; ■;', \cluni, 



from the same layer covering the suhumhrellar surface of the radial 

 canals (lig. 175), forming in either case conspicuous, often orange or red, 

 tliickeninc;s. Longitudinal ectodermal muscles move the tentacles in a 



