REPORT ON THE SIPHONOPHOR^E. 203 



Siphon (figs. 5, 6, s). — The large central polypite which represents the axial trunk of 

 the monogastric corm is composed of four distinct segments. The first and uppermost 

 segment, which corresponds to the pedicle of the siphons in the polygastric Siphonanthse, 

 is a vertical spindle-shaped tube which passes over above into the pneumatophore, below 

 into the basigaster. From this basal segment (at) arise three coronas of lateral appendages, 

 the upper corona of bracts (b), the middle corona of palpons (q), and the lower corona of 

 gonophores '(/, h). The second portion of the siphon is a pyriform basigaster (sb), the thick 

 exoderm wall of which is filled with cnidocysts. The third and largest segment (sm) is 

 the wide cylindrical or spindle-shaped stomach ; its thickened entoderm bears numerous 

 conical glandular villi, which usually contain one or two glossy, strongly refracting 

 globules (vacuoles ?). The fourth and last segment is the distal proboscis (sr), a very 

 contractile and muscular cylindrical tube which opens through the distal mouth ; this 

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



Tentacle (figs. 5, 6, t). — The single capturing filament, which arises from the base of the 

 siphon on its dorsal side, is a long cylindrical tube and bears a series of very numerous 

 tentilla. These are, composed of three parts, a slender proximal pedicle (fig. 8, ts), a broader 

 cnidoband in the middle (tk), and a simple thin terminal filament (tf). The cnidoband is 

 naked, without involucrum (as in Rhodophysa, ForsJcalia, and Halistemma) ; it is a 

 simple spiral, like a cork-screw, with four or five turns. 



Palpons (fig. 6, q) and Palpacles (r). — The palpons are attached to the axial trunk 

 immediately below the bracts and seem to correspond in number to the latter (fifteen to 

 twenty). They may perhaps be regarded as the dislocated manubria of the medusomes, 

 the transformed umbrellas of which are the bracts. Each palpon is a very retractile 

 cylindrical tube, tapering towards the two ends. The open proximal end is attached by 

 a short pedicle to the trunk and communicates with its cavity ; the closed distal end is 

 pointed and armed with a bunch of cnidocysts, and coloured with bright-red pigment- 

 spots. From the pedicle arises on its upper or dorsal side the palpacle, a long, thin, 

 simple filament, beset with small cnidocysts (fig. 6, r). 



Gonodendra. — Below the corona of palpons, between it and the basigaster (sb), is 

 attached to the trunk an annular group of small buds. These seem to develop into 

 gonophores ; but only two small gonodendra were developed in the specimen figured, 

 a male and a female. These were so disposed symmetrically, that the female gonophore 

 (fig. 6,/) occupied the right side, and the male gonophore (h) the left side of the basi- 

 gaster. The clustered gonophores were small and very numerous, with a well-developed 

 umbrella, four radial canals, and a ring-canal. The female manubrium is subspherical 

 and contains a single large ovum ; the male manubrium is club-shaped and the central 

 spadix surrounded by ripe sperm. 



