The porifera and coelentera . retainsconnection withthe more centralendoderm, bybending inwardsthrough the thickexumbral meso-gloea. This bentaxis, together withbands of cnido-blasts, which runfrom the marginalring already men-tioned to the pointof attachment ofthe tentacle, giverise to the char-acteristic mantlerivets orperonia. The musculature of the bell is of the usual type, except for thegreat development of radial muscle bands along the course of theradial canals through the subumbrella and pseudo-manubrium. In two out of the four families into which this group isdivided (Petasidae, Trac
The porifera and coelentera . retainsconnection withthe more centralendoderm, bybending inwardsthrough the thickexumbral meso-gloea. This bentaxis, together withbands of cnido-blasts, which runfrom the marginalring already men-tioned to the pointof attachment ofthe tentacle, giverise to the char-acteristic mantlerivets orperonia. The musculature of the bell is of the usual type, except for thegreat development of radial muscle bands along the course of theradial canals through the subumbrella and pseudo-manubrium. In two out of the four families into which this group isdivided (Petasidae, Trachynemidae) the general relations of partsof the medusoid are of the type already familiar (Fig, 5); butin the other two (Aglauridae, Geryonidae) the gastric cavitij doesnot lie in the subumbrella, but is situated at the distal end of theapparent manubrium ; the latter is really a prolongation of thesubumbrella, solid except for the radial canals, and may be termeda pserido-manuhrium. The mouth is generally surrounded by four. Fitt. 3b. Carmariiiu (Utiyuata) hastata (alter Haeckel). «, nerve fandcnidoblast ring; o, radial nerve and canal; I, tentaculocyst;c, circular canal; e, blind centripetal canal; y, ovar>-; h, peroniumor cartilaginous process from the cartilaginous marginof the disc centripetally in the outer surface of the jelly-like disc ;six of these are perradial, six interradial, corresponding to thetwelve solid larval tentacles, resembling those of Cunina; fc,dilatation (stomach) of the pseudo-manubrium; I, jelly of thedisc ; p, pseudo-manubrium ; t, tentacle (hollow and tertiary, by six perradial and six interradial solid larval tentacles);«, cartilaginous margin of the disc covered by thread cells; v,velum. (From Lankester.) 32 THE HYDROMEDUSAE (Aglantha) or six (Geryonia) short perradial lappets; in thePetasidae and Trachynemidae it opens through the short manu-brial cavity into the subumbral gastric cavity; in the Aglauridaeand Geryoni
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