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



sagittal section) was young and immature, the cormidia being without gonophores; but the 

 nectophores (ten in number) attached to the trunk, and the long tentacles (about thirty) 

 attached to the base of the siphons, were rather well preserved. This conn had a length 

 of 10 mm. and a breadth of 6 mm., two other corms (one of which is represented in fig. 

 18) were somewhat larger and bore a small clustered gonodendron (g) on each cormidium ; 

 but the nectophores (except one or two) were lost, and the siphons with the tentacles 

 detached ; the basal pedicle of the siphons only (s) had remained on the trunk. The 

 number of cormidia was forty to fifty. The length of these two corms was 16 to 20 mm., 

 the breadth 10 to 15 mm. The trunk of one corm was similar to that shown in figs. 39 

 and 40, that of the other relatively smaller (fig. 48). The fourth specimen was the 

 interesting monogastric larva shown in fig. 50 (Auronula). 



Auronula (fig. 50). — The remarkable larva— only a single specimen of which I could find, 

 after carefully examining the "Triton" collection — had a length of 4 mm. and a breadth 

 of 3 mm.; it represents a single medusome, the modified umbrella of which is the large, 

 flatly spheroidal pneumatophore (pa); the manubrium a single large central siphon (sc). 

 This protosiphon has a terminal mouth (ao), and bears attached to the dorsal side one single 

 tentacle (td), and above it a rather large aurophore (I). The relatively large size of this, 

 and the full development of its radial structure (lm), makes it perhaps probable that the 

 aurophore is not an independent medusoid person (a modified nectophore), but only a 

 separate basal organ of the pneumatophore. Besides some small buds on the ventral side, 

 no other organs were visible in this monogastric Auronula. Unfortunately it was not 

 well enough preserved to allow of a microtomic examination. 



Nectosome (figs. 39 and 48, lateral view, from the right side; fig. 40, vertical 

 sagittal section). — The superior or apical half of the corm is occupied by the large spheroidal 

 pneumatophore (p) and the corona of nectophores (n). This is bisected in the sagittal 

 plane by the aurophore (I) in the dorsal median line, and by a series of buds (i) in 

 the ventral median line. The aurophore is in this species just the same size as each of 

 the nectophores ; the number of these is ten to twelve. The structure of the aurophore 

 (/) and its axial pistdlum (lm) is the same as in Rlwdalia (PI. V.). 



Siphosome. — The inferior or basal half of the corm is occupied by the bulbous trunk of 

 the siphosome and the numerous cormidia attached to its outer surface. The cartilaginous 

 trunk (fig. 40, a), pierced by a dense network of anastomosing canals (ac), is sometimes 

 subspherical, at other times more like a spindle or a truncated cone. The axial canal (ca) 

 is twice as broad as its anastomosing irregular lateral branches, and opens below by the 

 primary mouth. Each cormidium bears a simple tentacle on the dorsal side of the 

 proximal base of the siphon (s), and in the mature corms a small gonodendron (fig. 49). 

 This is composed of a single androphore (h) and eight to twelve gynophores (f). The 

 gonopalpon seems to be rudimentary in this species. 



