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



of thin, flat cells in the distal half. The thin but firm supporting plate lying below the 

 sense club is very much thinned away in the distal half. The endodermal epithelium is 

 single-layered in the wide ampulla-like swollen basal half, but composed in the distal 

 half of from four to five layers of cells, placed one above the other (figs. 6, 7, ol'). Each of 

 these cells contains a small crystalline otolite {ol). As soon as we dissolve the calcareous 

 otolite in a drop of acid, we see plainly the stratified otolite cells, as w T ell as the csecal 

 distal end of the sense canals which leads with a double arching outwards as far as the 

 middle of the distal half of the rhopalium containing the otolite (fig. 6, radial longitudinal 

 section ; fig. 7, oblkpie nearly horizontal section). 



The gastrovascular system (PI. XXX. fig. 1) of Drymonema, is constructed essentially 

 on the same hereditary family type as that of all other Cyaneidas, but is distinguished 

 individually from the rest in a very striking manner, corresponding to the peculiar 

 transformation of the umbrella corona. The formation of the branched pouches of the 

 peripheric coronal intestine in the latter is in especial very peculiar, whilst the conforma- 

 tion of the central principal intestine and its oral organs do not vary essentially from 

 those of Cyanea. 



The central principal intestine consists of a flat discoid central stomach, having the 

 oral cross with its appendages in the centre below, whilst its peripheric margin opens 

 into the pouch corona of the coronal intestine. The sharp, peripheric margin of the 

 central stomach shows sixteen projecting corners, corresponding to the sixteen radial 

 pouches opening into it and the sixteen subradial septa or cathammal ridges by which 

 these are separated from each other. The largest diameter of the margin amounts to 

 from one-third to one-fourth that of the whole umbrella. Its upper aboral wall, or the roof 

 of the stomach, is formed by the smooth endodermal surface of the thick firm cartilage- 

 like central gelatinous disk ; it is traversed by fine radial furrows, which run out from a 

 central four-lobed coronal furrow and are dichotomised towards the periphery. The lower 

 or oral wall of the discoid central stomach, or the bottom of the stomach, is formed by the 

 thinner but equally firm, cartilage-like peristom disk. The central oral cross (figs. 

 1, 9), whose four perradial limbs pass into the deep oral grooves on the axial surface of 

 the oral curtains, opens into the middle of the peristom disk. The wall of the cruciform 

 oral opening forms a very firm, thick cartilaginous oral ring, as in Cyanea. The latter 

 passes at the four perradial limbs of the oral cross below into the cartilaginous abaxial wall 

 of the arm grooves on the one hand, and outward into the four strong cartilaginous oral 

 pillars on the other. These pillars divide the peristom area into four interradial arese, 

 which are occupied by the delicate, thin-membraned gastrogenital membrane (gg), 

 and from which the four genitalia hang down as four wide, folded csecal pouches (fig. 9, s). 



The oral curtains, or arm curtains, comport themselves on the whole the same as in 

 Cyanea and Desmonema (System, p. 522, taf. xxx. fig. 1-3). They form four powerful, 

 very broad, thin-walled membranes of a roundish triangular outline, whose proximal 



