lxiv THE VOYAGE OF H.M.S. CHALLENGER. 



is occupied more or less by the oesophagus and the different organs of buccal stomach and 

 also often by the genitalia. 



§ 92. Niches of the umbrella cavity (" cavernulae subumbrales "). In many Medusae 

 special secondary spaces are developed on the subumbral wall of the umbrella cavity, 

 partly by the formation of folds or projections of the subumbrella, partly by the insertion 

 of single organs into pit-like depressions and partly by peculiar conditions of growth of 

 the umbrella margin and the " marginal bodies " lying on it. All these different second- 

 ary cavities of the umbrella cavity may be placed together as " niches of the umbrella 

 cavity or subumbral niches " (" cavernulae subumbrales "). In many Narcomedusae, 

 namely the Peganthidae, the cavity of the umbrella corona is divided into a peripheric 

 corona of separate "lobe cavities" (" cavernulae lobares"), which surround the central 

 umbrella cavity like the altar niches of a round temple (JPegantha pantheon, p. 37, 

 Pis. XL, XII.). In Pedis, eight adradial " oral funnels or inner buccal pouches " (" caver- 

 nulae buccales ") are invaginated from outside into the oesophagus (p. 15, Pis. IV., V. figs. 

 4, 5, io). In many Cubornedusse and Peromedusae, namely, the Periphyllidas, each tentacle 

 is surrounded at its base by a subumbral tentacle funnel (" cavernula tentacularis "), over 

 which the distal margin of the subumbral coronal muscle projects like a roof. In Periphjlla 

 (PI. XIX. fig. 6, PL XX. fig. 8) it is simple; in Periphema (PI. XXIV. fig. 1) it is divided 

 into secondary funnels by a number of small frenula. In many Cubomedusas, four perradial 

 triangular subumbral folds pass as " frenula velarii " from the base of the sense niche and 

 the vertical septum of the marginal pouches to the subumbral surface of the horizontal 

 inwardly projecting velarium (PI. XXVI. figs. 2, 3, 8, irf ), so that two small velar niches 

 (" cavernulae velares ") are inserted on each side of the velarium. In most Discomedusae 

 eight (more rarely sixteen) sense niches are formed on the umbrella margin for the recep- 

 tion of the sense clubs or rhopalia ("antra rhopalaria," comp. above, § 86). In some 

 species, e.g., in Drymonema, these stretch centripetally far into the subumbrella (Pis. 

 XXX., XXXL, cm). 



§ 93. Coronal cavity of the umbrella and funnel cavity of the umbrella. In some 

 Craspedotae, or in many Acraspedae, four or eight vertical folds of the subumbrella, the 

 mesenteries (" mesenteria ") are developed in the bottom of the umbrella cavity at the 

 base of the oesophagus, and the upper part of the simple umbrella cavity is thus divided 

 into four or eight separate cavities, the umbrella funnels or funnel cavities (" infundi- 

 bula," i). We therefore term the lower, simple half of the umbrella cavity, which opens 

 freely below at the umbrella margin, the coronal cavity of the umbrella (" antrum 

 coronare "), and the upper quadrilocular or octolocular half as the funnel cavity of the 

 umbrella ("antrum infundibulare"); the former communicate with the latter by four 

 interradial or eight adradial funnel openings (" ostia infundibularia "). 



§ 94. Funnel cavities and mesenteries (" infundibula and mesenteria "). The four or 

 eight funnel cavities or umbrella funnels (" infundibula," i), which compose the umbrella 



