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



(figs. 3, 4, oJc), lie on the inner side of the tentacles between their insertion and the 

 basis of the velum. In some places they alternate with the tentacles, but are usually 

 irregularly distributed. Their number appears very variable. In one of the three speci- 

 mens before me there are very few (20 to 30), in the second above 100, and in the third 

 over 200. The opaque marginal clubs appear chalk-white in reflected light, black in 

 transmitted light. They are pyriform, gradually enlarging from a narrow stalked base 

 about one-third to one-half as long as the basal bulbs of the marginal filaments, - 6 to - 8, 

 at the most 1 mm. long and 0"3 mm. broad. Treated with acid, they show a narrow 

 canal (fig. 8). The velum (r) is rather broad, but very thin and delicate, and with 

 many folds. The system of circular muscles of the subumbrella is moderately developed, 

 and shows no special peculiarities. The umbrella cavity is very shallow, its upper half 

 filled up in a great measure by the stomach and the four genitalia. 



The wide oral opening leads into a short, shallow gastral sac, whose four basal 

 corners are extended into four conical funnels. These pass into the four radial canals, 

 which are pinnated in their proximal half and bear the genitalia (figs. 1, 2). The narrow 

 radial canals open at the umbrella margin into an annular canal, which sends branches 

 into the tentacles and marginal clubs (fig. 8). 



The oral opening (figs. 1,2 in the centre) is quadrate, very wide, with irregularly 

 frilled borders, extending at the four perradial corners into four short wavy oral lobes 

 (fig. 2, al). The thin transparent wall of the quadrangularly prismatic gastral tube 

 hangs down nearly to the middle of the umbrella cavity ; its lower free oral margin is 

 much thinner. A perradial cross (fig. 2, g) whose four limbs are - 5 mm. broad and 

 8 mm. long, appears very plainly in the fundus of the stomach on the gastral surface of 

 the gelatinous umbrella. This cross is formed by four very narrow ciliated grooves which 

 are centripetal processes of the umbrella wall of the four radial canals. In one of the 

 three examples the four limbs of the cross meet in the aboral centre-point of the sub- 

 umbrella, so that the quadrate ground of the stomach is divided into four congruent 

 equally limbed triangles (fig. 2). In the other two examples the points of the two 

 opposite triangles are truncated and rest (at one specimen at the length of 2 mm. in the 

 other at 6 mm.) in such a way that opposite points of the two other alternating 

 triangles remain at about the same distance from each other (fig. 7). The geometrical 

 form of the ciliated cross is here plainly amphitect, whilst it is completely regular in the 

 first specimen (fig. 2). 



The four perradial corners of the fundus of the stomach are prolonged into four 

 conical funnels (fig. 2, ck) whose ends extend to the middle of the genitalia and 

 occupy the proximal half of the radial canals. The latter are very broad in the proxi- 

 mal half, and, on the other hand, very narrow in the distal half below the genitalia. In 

 the middle of its course each radial canal gives out a number of alternating pinnated 

 branches, twenty to thirty on each side, at right angles at the two edges (fig. 5). These 



