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



with or without gastra] filaments) is already present in the corresponding sections of 

 the class Polypi, from which the Medusae are descended. The lower Hydropolyps (from 

 which the Craspedotae or Hydromedusae) are descended, never possess the four 

 characteristic interradial taeniola of the Scyphopolyps, although similar longitudinal 

 ridges of the inner gastral wall (more irregular in number, form and position) are also 

 found in some Craspedotae (Tubulariae, &c). On the other hand, the higher Scyphopolyps 

 from which the Acraspedae (or Scyphopolyps) are descended, are all originally dis- 

 tinguished by the presence of the four interradial taeniola (also called " gastral walls, 

 mesenteric swellings, longitudinal ridges, longitudinal walls, longitudinal swellings of 

 the inner gastral wall "). These longitudinal gastral ridges (which are also universal 

 among the corals as the so-called mesenteric filaments or mesenteric bands, more 

 properly " gastral bands "), appear originally in the Scyphopolyps as four interradial rib- 

 like thickenings of the gelatinous supporting plate or fulcral lamella ; they project from the 

 inner surface of the gastral wall freely into the gastral cavity, and in this way divide its 

 peripheric hollow space into four perradial niches or grooves (PI. XV. figs. 2, 3, 7, 8, ft ; 

 PI. XVII. figs. 13, 14, ft). They usually contain a longitudinal muscle (PI. XVII. fig. 13, 

 on) and are always covered by endodermal epithelium. 



§ 106. Dorsal and ventral taeniola (" taeniola notumbralia" and " ccelumbralia "). As 

 the taeniola or gastral ridges of the Scyphopolyps are developed over the whole extent of 

 their gastral surface and originally (in Scyphostoma, Sjiongicola, &c.,) run from theaboral 

 to the oral pole, from the foot plate of the peduncle to the margin of the mouth, we 

 must divide them into two principal sections, a notumbral part and a ccelumbral part ; 

 these two pass into one another at the peristom margin or calyx margin of the 

 Scyphopolyps (corresponding to the umbrella margin of the Scyphomedusae). The 

 notumbral or dorsal tamiolum reaches from the aboral base or point of the cone to the 

 peristomial margin or umbrella margin, and is a ridge-like thickening of the calyx or 

 " notumbrella " (covered with dorsal endoderm). The ccelumbral or ventral taeniolum 

 reaches from the peristomial margin to the umbrella margin, and is a ridge-like thickening 

 of the " ccelumbrella " covered with ventral endoderm. The cathamma or septa of the 

 Acraspedae (k) are formed at the points where the two portions of the taeniola, the dorsal 

 and the -ventral ridges, come in contact and become fused. 



§ 107. Gastral filaments (mesenteric filaments, internal gastral tentacles, f). The 

 characteristic " gastral filaments " of the Acraspedae, which are universally present in 

 them and totally wanting in the Craspedotae, are originally papillae or excrescences of 

 the taeniola. We immediately perceive from such Acraspedae, in which the taeniola 

 persist in their original form (especially Stauromedusae) that the filaments are originally 

 parts of the taeniola (Tesserantha, PI. XV. ; Lucemaria, PI. XVI., XVII). This is also the 

 case in the strobilation of the Discornedusae, where the separate parts of the four strobila 

 taeniola are immediately transformed into the four primary filaments of the Ephyrula 



