REPORT ON THE DEEP-SEA MEDUSJE. 77 



broadest in the middle, lanceolate above and below (figs. 8, 12, gn). They communicate 

 with the simple central space of the basal stomach by four narrower longitudinal clefts, 

 and correspond to the four peduncle chambers of Lucernaria (Pis. XVI., XV 1 1., gn). 

 The transverse section is therefore the same in both cases, and shows the form of a 

 Maltese cross ; but with this difference, that in Lucernaria (PI. XVII. fig. 13) as in Peri- 

 colpa and Peripalma the four interradial tseniola are solid selvages, whilst in PeriphgUa 

 (PI. XXI. fig. 14) as in Periphema and Pericrgpta they are hollow cones. Two diverging 

 phacelli (or longitudinal rows of gastral filaments) beset the entire length of the hollow 

 cone, and diverge from each other below at the pylorus, in such a way that the two 

 phacelli of each two adjacent cones which are turned to each other meet in the four 

 perradial angles of the pylorus. From thence they diverge further upon the margin of 

 the gastral openings. 



The tseniola ("tasniola gastralia," gastral longitudinal selvages, ft). The axial princijml 

 intestine of PeriphgUa, whose three divisions have been already described, has apparently 

 an extremely complicated character, which separates it in a striking manner from 

 other Medusas. A clear, simple explanation of this may, however, be gained by com- 

 paring this axial intestine with the more simple principal intestine of the Lucerna- 

 rida3 and Tesseridse. If we abstract the secondary differentiations, and only bring 

 forward the primary principal conditions, we are able to refer all these formations 

 to the simple, common ancestral form, to the primary intestine of the scyphopolyps, 

 Scgphostoma (comp. my System der Medusen, pp. 364, 3G7, 384, 403, &c). The four 

 endodermal interradial tseniola are already developed from this primary intestine, divide 

 the periphery into four perradial niches or pouches, and traverse the whole length of the 

 gastral wall, from the aboral peduncle base to the oral margin. These then charac- 

 terise pre-eminently the section of the Acraspedas, and develop the peculiar typical 

 " gastral filaments." In their common parent form, Tessera as in Scgphostoma, we can 

 distinguish two sections in each tseniolum, the umbral at the umbrella wall and the sub- 

 unibral at the peristome wall ; the two touch at the umbrella margin. From beginning to 

 end, from the aboral central point to the oral margin, the interradial tgeniola and their 

 products show a steady tendency to centripetal growth, whilst on the contrary the 

 perradial pouches between them show the same tendency to centripetal growth. In our 

 PeriphgUa (1) the four funnels of the basal stomach and their rows of filaments, (2) the 

 obehsk plates of the central stomach with rows of filaments, (3) the buccal columns of the 

 buccal stomach with their wings and oral filaments belong to the centripetal system of 

 the four interradial taeniola. On the other hand, (1) the four niches of the basal stomach, 

 (2) the gastral openings of the central stomach leading into the peripheric coronal 

 intestine, (3) the buccal pouches and wing pouches of the buccal stomach belong to the 

 centrifugal system of the four perradial pouches. The correctness of this view is proved 

 directly by the distribution of the eight phacelli or rows of filaments, of which each two 



