■220 



Ca'LKXTKRATA 



diviihuils in !;rouiis wliirh frrquonllv scparaU- Ih'I'.m'c liccoiiiinL; maliirc, were once 

 rei^anlcd as ilistiiun animals. I'my,!, Ih ph y<s-'' ilii;. iSjl, in \\arnicr seas. 

 Snli Or.lcr 111. C\'S 1"( >M-'.CT.K. V\oM greally enlar.u'eil; llu- eienosareal 

 tube redueeil, llie ini]i\ iiluals nio enveriin:; scales nni- swimniin.L; bells) allaelieil 

 to under side of ihe lloal. Ph vsoliii* \\<r{uy:uv^c nian-of-war, slin.us se\erely. 

 Sub (tnliT W. lUSC(^X.\\'ril.lv I'loal a llallencl dise; manubrium pro- 

 jects from centre of lower surfaee. /'('/•/'//(//'•disc. ]\li;'Ui'-''' (liij;. iSj). 



Class II. Scyphozoa (Scyphomeduss). 



Tlie Scyiiho.'.oa parallel the ]I}-dro;:oa in fre(|uenlly lia\ing an altcr- 

 nialion. of generalions; the asexual generation beinu; the Si-yplio polyp or 

 scvplioslonni, the sexual an aeraspedotc medusa. In contrast to the 

 Hydrozoa the asexual stage pla)-s a subordinate role; it is closely similar 

 in all species, and can e\"en be lost [rflai^ia), while the medusa- are ahva^'s 

 well developed and present great variel\- of form. 



The scyphostoma (figs. 1S3, 184) recalls Hydra, but lias a small 

 perisarcal cup around the aboral end. Internally there are four longi- 

 tudinal folds projecting into the gaslral cavity and extending from the 



1-iG. iS:;. Fie.. iS.j. 



Fig. iS;,. — Scy]ihos(oriia of Aurcli.i aurila (from Korsclu'll-IIcidcrV k. jx-risarc 

 cu|i; [>h, jirol^oscis; .v, slalk; /, t^asU-al folds; /r, ci. lodcrmal fiiuiu'ls. 



l''ic.. 1S4. — .Scelion of Scyphostoma l^from llatschck'). j;r, gasU-ie pouelies; .s", 

 gastric sejita; siii, muscles. 



margin of the mouth to the opposite pole. These septa or tu-niohr 

 (lig. 184, s) appear in cross-seclioit as small folds of entoderm supported 

 l.)y a process of the supporting layer containing a muscle band c.xtcMiding 

 down from the peristome (lig. 184). Thev are important morpholog- 

 ically, since in hudtling they produce the gastral tentacles [phacdhc) of 

 the medusa'. Further, they are the lirst appearance of the septal system, 

 so strongly developed in the Anthozoa. 



The me<lusa' are large (four inches to four feet or more in diameter) 

 with a slightly arched umbrella, often of almost cartilaginous consistency. 



