REPORT ON THE STPHONOPHORJS. 317 



gonodendron are produced by budding. Each branch of the gonostyle is a secondary 

 cormidium, composed of a sterile distal palpon, a large female medusome, and a group of 

 clustered small male medusomes. 



Pneumatophore (fig. 5, £>). — The float is pyriform, 3 mm. long and 2 mm. broad, 

 with a red pigment-cap in the apical third. The enclosed pneumatocyst is subspherical, 

 1 "2 to 1 "5 mm. in diameter ; it fills the upper or apical portion of the air-sac, which is 

 separated by an annular diaphragm (pylorus infundibuli) from the spheroidal lower or 

 basal portion, the air-funnel. This is lined by the greenish hypocystic tapetum, which 

 also enters by the pylorus into the cavity of the air-flask and lines its basal third as 

 endocystic tapetum. No radial septa or villi arise from the air-funnel. 



Siphon (fig. 5, s). — The single siphon of the monogastric cormidium is spindle-shaped, 

 6 to 9 mm. long and 2 to 3 mm. broad. Its ampullaceous basal portion (basigaster) is 

 attached by a short pedicle to the base of the pneumatophore. The dilated middle 

 portion, or the stomach, is covered inside with numerous yellowish-brown hepatic villi 

 (sh). The thin tubular proboscis (sr) is very muscular and opens by a mouth, which 

 may be expanded in the form of a circular suctorial disc (ss). 



Tentacle (fig. 5). — The single tentacle (t) which arises from the base of the siphon, 

 on its dorsal side, is a slender cylindrical tube, beset with a series of tentilla. These 

 are simple cylindrical filaments, and bear on their dorsal side a multiple series of cnido- 

 cysts ; the structure is similar to that of Nectophysa (PL XXIII. figs. 5, 6). 



Palpons (fig. 5). — The corona of rose-coloured tasters which protects the siphosome 

 is attached to its base, immediately beyond the nectosome. It is composed of about 

 thirty spindle-shaped palpons, besides the small buds of young ones. Their pointed 

 distal end is closed, whilst the proximal end of their cavity communicates with the 

 pedicular canal of the siphon. 



Gonodendron (fig. 5, gd). — The single large clustered gonodendron, which is attached 

 to the base of the siphon, on its ventral side, is similar to that of the Rhizophysidse. 

 The gonostyle is richly branched, and each ultimate branch bears a single gonopalpon on 

 its distal end (PI. XXIII. fig. 8, gq). and above it a single medusiform gynophore (/) 

 and a cluster of several (four to eight) ovate androphores (h). 



Family XXI. Ehizophysid^;, Brandt. 1835. 



Rhizophysidx, Brandt, Prodromus description^, &c, 25, p. 33. 



Definition. — Cystonectse polygastricse, with a long tubular trunk of the siphosome, 

 bearing in its ventral median line numerous monogastric cormidia, separated by free 

 internodes. Each cormidium with a single siphon and a single tentacle. Pneumato- 

 saccus large, without radial septa and pericystic radial pouches, but with eight or 

 more radial groups of hypocystic villi. 



