TIM A FORMOSA L. AGASSIZ 



FIG. 6. Schematic section through a hydromedusa in the region of the 

 velum after Delage and Herouard (Zoologie Concrete), cnlc, circular canal; 

 cntt, tentacular canal; msg, mesoglcea; cnr, radial canal; mslso, muscular 

 fibres of subumbrella; mcht, muscular fibres of velum; brt, nettle cell battery; 

 nc, external nervous ring; ni, internal nervous ring. 



eight adradial tentacles. Of the remaining sixteen tentacles, 

 eight are per-adradial (halfway between a per-radial and adra- 

 dial tentacle) and eight interadradial (halfway between an in- 

 terradial and an adradial tentacle). 



Body layers. The body of the medusa is composed of 



