THE HYDROMEDUSAE 



47 



fioiii ubservatioiis on u few forms which ;ire too widelv' ditlereiit to 

 allow of a general developnieiital .scheme being as yet laid down. 

 A plaimla i.s apj)arently always formed ; the first individual liuddcd 

 fioni it may 1>e a i)nenmato))hore (Halistemma), nectocalyx 

 (Ei)ibulia), or hydrophy Ilium (Agalma). The coenosarc may be 

 a lateral extension of the first gastrozooid (Cystonectae), or may 

 be its elongated stem (? Physophoiidae, Calyconectae). 



Appendix to Hydromedisae. Xo. I. 

 Limnocodium mul Limnocnida. 



Tliese are two freshwater medusae, the first-named known only from 

 tlip Victoria Rpj,na Tank of the Royal Botanic Society in London, the 



•VJ. — IJiiiiiocfxliuiii, iiK sefii floating, x h. MJ{, marginal niTve ami ciiiiloblast ring ; Tc, 

 vluni : IT, iicrnidial tcntiicle. (After I^nkester.) 



.')H. - I'(ily])s of Liiniiocodiiiiii on WHed (after A. G. Bonme). 



.'i4.- l)i;i).T;iiii of tliH sense orgaiLS of Lininocodiuni and.Lininocni<la. C, cavity of tlin 

 vesicle, «liiili in Linniocodinni in continued as a canal into the velniii ; EC, ecto<leni) of the, 

 .sense ori;un ; At', ecto<lennal linin^r of the vesicle ; KN, refringent endodenn cells of the sense 

 organ ; A,'.V', granular endcjderni cells of the sense organ ; KX", position of endodenn of the cir- 

 cular canal. (After Lankester and (iiinther.) 



second known only from Lake Tanganyika. They undoubtedly belong to 

 the Hydronicdu.sae, and to ditferent orders of the clas.s, but it is still a 

 matter of dithculty to assign them to any of the existing orders. 



Limnocnida (Fig. 55) ])re8ents points of resemblance both to Antho- 

 niedusae and to Xarcomedusae. It shares the manubrial position of its 

 generative organs with both these ortlers ; but in tlie shortness of the 



