REPORT ON THE DEEP-SEA MEDUSAE. lxv 



funnel cavity of many Medusae, are hollow spaces, more or less conical and lined by the 

 ectoderm of the subumbrella ; they are always csecal in the aboral bottom of the umbrella 

 cavity, whilst they open into the coronal cavity of the umbrella by the roundish funnel 

 openings (" ostia infundibularia "). The adjacent funnels are separated by thin vertical 

 septa, the mesenteries (" mesenteria " or " mesogonia," ivr). In one group only, the 

 Pectyllidas (Pis. III.— VIII.). there are eight mesenteries present (four perradial and four 

 interradial) between eight adradial funnels. Otherwise there are invariably only four 

 perradial mesenteries between four interradial funnels. The mesenteries or mesogonia 

 are formed by the four perradial oral corners extending, like wings, in the bottom of the 

 umbrella cavity and rising in the form of thin folds of the subumbrella. The further 

 these folds pass towards the outside on the subumbral surface, and the further they pass 

 downwards on the oral corners, the deeper are the intermediate funnel cavities. In the 

 Craspedotae, the mesenteries are always thin, delicate membranes, which serve chiefly for 

 fixing the oesophagus {e.g., among the Anthomedusae in Tiara and Turris, System, taf. 

 iii., iv. ; among the Trachomedusae in Pectyllis and Pectanthus, Pis. IV., VIII.). In the 

 Acraspedae, on the other hand, the mesenteries are often hollow, as the central gastral 

 cavity arches into them like pouches, especially in part of the Lucemaridse ("mesogonial 

 pouches," " bursae mesenteriales "). The funnel cavities are usually flat and insignificant 

 in the CubomedusEe (PL XXVI.), but very large and deep in the Peromedusae. In the 

 Periphyllidae (PI. XXI. figs. 12, 13, ib), they even ascend as far as the point of the 

 umbrella cone, so that they touch the four interradial taeniola, in the centre point of the 

 basal stomach (PI. XX. fig. 8, ib). In such a case, the funnels hollow out the entire 

 length of the four interradial taeniola, so that these solid ridges are transformed into 

 hollow cones. The four interradial funnel cavities are peculiarly modified in the Dis- 

 comedusae, where they obtain special importance as "respiratory cavities" or " subgenital 

 cavities." 



§95. Subgenital cavities (" demnia," otherwise also called "respiratory cavities," 

 "genital cavities," "umbrella cavities of the reproductive organs," " infundibula sub- 

 genitalia "). These four peculiar interradial cavities are only found in the order of the 

 Discomedusaa, where they are in part developed and transformed into peculiarly shaped 

 hollow spaces. Fundamentally they are merely subumbral funnel cavities, which have 

 acquired a varied form and function by special adaptation (namely in their relations to 

 the genitalia). Whilst in the three orders of the Tesseroniae, the four funnels usually 

 rise as slender, hollow cones, corresponding to the conical or pyramidal form of the high, 

 vaulted umbrella, in the Ephyroniae or Discomedusse, on the contrary, they extend on 

 the lower surface of the umbrella, in the form of low pouches, in correlation to its flat 

 discoid shape. In this order the subumbral wall of the flat, wide gastral cavity is, at 

 the same time, the place of origin of the reproductive glands, and forms a delicate thin- 

 walled "gastrogenital membrane" (gg), in which the four interradial (in the Cannostomae 



(ZOOL. CHALL. EXP. PART XII. — 1881.) M i 



