234 



CGELENTERATA. 



by budding. These, the medusae, may separate early from the 

 colony and swim freely. A medusa (figs. 178, 179) has the form 



FIG. 178. Rhopalonema velatum. c, ring canal; e, exumbrella; g, gonads; h, otocysts: 

 m, stomach; n, nerve ring; o, mouth; s, subumbrella; t', t'\ tentacles of first 

 and second order ; v, velum. 



of a dome-like or disc-like bell and consists chiefly of an ex- 

 traordinarily watery jelly. The bell or umbrella of the medusa is 

 covered on both its surfaces the concave or subuinbrella, the con- 



