REPORT ON THE DEEP-SEA MEDUSAE. 99 



arisen by fusion of the umbral and suburnbral wall of the primitive stomach of the 

 Scyphostoina, (" cathamma," h). The remains of the gastral epithelium are therefore 

 visible in the transverse section of the selvages, in the form of the " enclodermal lamella, 

 cathammal plate, or vascular plate" (fig. 10, hp), which separates the thicker gelatinous 

 disc of the umbrella (ug), from the thinner supporting lamella of the subuinbrella (zw). 

 We can even distinctly distinguish two layers of cells in the gastral plate, of which the outer 

 belongs to the umbral endoderm, the inner to the suburnbral endoderm. A leaf-shaped 

 genitalium, which projects freely into the contiguous radial pouch, is fastened along the 

 entire length of the septal selvages on each side of its suburnbral part (fig. 10, s). 



Four margins and two walls can be distinguished in each radial pouch. Whilst the 

 two lateral margins of the quadrangular pouch are formed by the interradial septal 

 selvages, its lower (or distal) margin is the proximal velar margin and its upper (or 

 proximal) margin is the gastral opening. The latter can be completely closed by the 

 perradial pouch-valve ; this is formed by a horizontal fold of the subumbrella, which 

 rises at the upper margin of the pouch and projects as a thickened gelatinous plate freely 

 into the cavity of the basal stomach. The external or abaxial wall of the radial pouches 

 is formed by the smooth enclodermal surface of the gelatinous umbrella, its inner or axial 

 wall by the delicate subumbrella. The latter is thin-walled and very extensible, and 

 consists from within to without of the usual four layers: — (1) The enclodermal 

 epithelium with high, glandular, cylindrical cells (fig. 10, dw) ; (2) the thin but firm sup- 

 porting plate or gelatinous lamella (zw) ; (3) the muscular plate (mw) ; and (4) the 

 exodermal epithelium (qw). Although pretty firm, the suburnbral wall is so thin that it 

 stretches, like a delicate vefl, above the pouches, and allows all the organs lying in them 

 to shine clearly through. A narrow band-shaped longitudinal muscle (fig. 3, mp) runs 

 in its perradial middle line. This muscle passes above into the " mesogonium," or upper 

 supensory, below into the " frenulum velarii," or lower supensory. The latter divides the 

 distal section of each of the radial pouches into two broad adradial lobe pouches. 



The eight lobe pouches or marginal pouches (" bursse lobares," or " marginales," figs. 

 2, 3 8, bin) are caused by a perradial septum, which, running from each rhopalar niche 

 to the upper velar margin, divides the distal part of each radial pouch into two halves. 

 This septum is merely the abaxial margin of the frenula itself in w T hich the umbral and 

 suburnbral walls of the pouch are fused together. Each of the marginal pouches thus 

 formed is rectangular, nearly twice as broad as high. Dendritic, csecal, velar canals run 

 from their lower or distal margin into the "velarium" (fig. 8, cv). These lie entirely 

 in the thickened supporting lamella of the velarium, and are flattened like a ribbon ; 

 their endoclermal epithelium, like that of the radial pouches, is flat and clear on the 

 umbral side, high and glandular on the suburnbral. Their ramification is delicately 

 dendritic and is weaker towards the perradius, stronger towards the interradius. There 

 are forty-eight velar canals on the whole, so that twelve of them come on each 



