S 6 DISCOVERY REPORTS 



measures: pedicel i mm., cnidoband 2-5 mm., filament 5 mm. in length. In young stages the tentilla 

 are finger-shaped, with a patch of large, pavement-epithelial cells over the developing cnidoband: 

 the three sections show histological differences at an early stage. The filament contains numerous 

 smaller ovoid nematocysts (? isorhizas) measuring 18/x in length and 5/x in diameter, as well as larger 

 ovoid nematocysts, type unidentified, measuring 18 x 13/x. The cnidoband has on each side a row of 

 about 125 large nematocysts (? mastigophores) measuring 50x20/^. In between these are about 

 5000 finger-shaped nematocysts (? anisorhizas) regularly arranged in a dozen rows measuring jn 

 in diameter and 40^ in length. Their outer ends, which form a pavement, are overlain by large 



C.rad.d. 



Crad/at 



C.po 



C.ped 



"Crodv. 



Crad.v Cro'dlot 



C.ped c)pa 



Text-fig. 20. Marrus antarcticus gen.n., sp.n., 'Discovery II' St. 943, 1000-750111. Nectophore; A, underside; B, upper 

 side; C, lateral view; D, adaxial view, x 4-6. The muscular lamella is attached along the pecked continuation of the 

 pedicular canal. 



polygonal, epithelial cells measuring 0-04 x 0-02 mm. Often the exploded cnidoband may be found 

 on bracts. Palpons are of the same length as siphons, but more slender. No filament has been 

 observed at the base. Some of them, probably all, arise from the gonodendra. Gonophores observed 

 have all been female and monovon (Text-fig. 21 E). The largest eggs measure about 1-25 mm. in 

 diameter. The position of the gonophores relative to the gastrozooids has not been determined. 

 Dissection of female gonophores with a micro-manipulator showed that the endoderm of the outer 

 thin coat (umbrella) forms four or more radial canals, and that there is no terminal opening. Inside 

 this outer tunic is another, formed by the irregularly branched spadix (manubrium) (cf. Vogt, 1854, 

 Tab. 10, fig. 25; and Huxley, 1859, pi. vi, figs. 13, 14; pi. ix, fig. 14) that is flattened out by the large 

 ovum. When the ovum is partly grown the spadix grows up to one side of it and wraps branches 



