424 



CTENOPHORA 



a short blind canal, which terminates in an ampulla bearing two 

 statoliths supported by elastic processes from the ampullar 

 epithelium. 



The sub-umbrellar cavity extends for a distance of about one- 

 half the height of the bell. The mouth (i/), which opens into 

 this cavity, leads into a wide cavity that gives off a short blind 

 canal to the side of each tentacular sheath, and a straight tube 

 that leads straight to the statocyst, where it also ends blindly. 



Fig. 184. — Uydroctena 



ah, Aboral organ ; M, manubrium ; t, tentacle ; 

 F, velum. (After Dawydoff.) 



There are no radial canals and no ring canal at the margin of 

 the umbrella. There are also no ctenophoral plates. In the 

 absence of any information concerning the position of the genital 

 glands, the character of the epithelium of the tentacles and the 

 development, we are not justified in regarding Hydroctena either 

 as a Ctenophore or as a connecting link between the Cteno- 

 phora and the Hydromedusae. It may be regarded simply as a 

 Craspedote Medusa, probably related to the Narcomedusae, with 

 a remarkable aberrant aboral sense-organ. 



