260 JELLY-FISH, STAR-FISII, AND SEA-URCHINS. 



tube-feet in the ray. This common or radial tube 

 itself opens into a circular tube (Fig, 30, e) sur- 

 rounding the mouth of the animal (Fig. 86 m). This 

 circular tube therefore receives five radial tubes — 

 one from each of the live rays — and is likewise in 

 communication with a number of membraneous sacs 

 (Fig. 36, c, d), resembling in their structure (though 



Fig. 36. — Dagram of ambuldcral sv^lem of a Star-fish : a, madreporic canal; h, 

 inner end; g. outer end ot sums leadinc; to tircular neural vessel , h, from which 

 radial neural vessels, I, .irise ; c d, Folun vehicles ^/, ampulhc •, m, oval aperture; 

 n. madreporic plate. 



larger in size) those which occur at the base of each 

 of the tube-feet. The function both of these sacs 

 and of those at the base of each tube-foot is the 

 same, namely, that of acting as reservoirs of the 

 fluid when this is expelled from the tube-feet. 



