MEDUSAE. I; 



33 



into the main canal. Accordingly, each of the four radial canals of the mednsa has actually only two 

 gonadial bands, separated in the median line of the canal, but each of these bands is folded in a 

 complicated manner. The free edge of each of the pouches gives rise to a row of papillae of different 

 length (Plate III, fig. 2). The papillae are hollow; they are extensions from the lateral branches of the 

 radial canal, and their lumen communicates with the lumen of the latter (Plate III, fig. 5). The papillae 

 are more closely set in the distal part of each of the lamellae; in the middle part they .are more dis- 

 persed, and in the proximal part the edge of the lamella is smooth (Plate III, fig. 2). On the shorter 

 (younger) lamellae the smooth part is comparatively long, only a few papillae being present, and these 

 are distally situated; on the longest (oldest) lamellae the smooth part is quite short; on the quite young 

 lamellae no papillae are found, the edge is quite smooth. -- The oldest lamellae are in the middle part 

 of the system; the proximal and the distal lamellae are the younger. New lamellae are formed, how- 

 ever, not merely proximally and distally, but also intermediary between the older lamellae in any 

 spare room in the system. The side-walls of the lamellae are, as a fule, not quite plane, but are 

 more or less uneven. We may even, occasionally, find a secondary branch, forming an acute angle 

 with the mother-branch. -- In the present specimen the ventral, funnel-shaped part of the radial canals 

 reaches nearly to the distal end of the folded system. 



The bell margin carries a large number of tentacles and cordyli. In the present specimen there 

 are 400500 tentacles. Each of the tentacles has a somewhat compressed bulb, about 2.5 mm long; 

 this bulb is somewhat broader distally than proximally. Its outer (abaxial) edge is convex, the inner 

 (adaxial) edge is straight or faintly concave (Plate III, fig. 6). The distal end of the bulbus . bends 

 sharply inwards (adaxially) at the point of transition into the thread-like part of the tentacle; very 

 soon the latter bends sharply outwards. The tentacular bulb is hollow; its lumen opens like a funnel 

 into the circular vessel. On the abaxial side of the basal part of the bulb there is a short, conical 

 protuberance (a rudimentary tentacular spur) extending into the gelatinous substance of the ex- 

 umbrella (Plate III, fig. 6). - - The cordyli are small; in the present specimen they are about V B tne 

 length of the tentacular bulbs. They alternate fairly regularly with the tentacles, forming a row a little 

 inside the row of tentacles. Each of the cordyli has the shape of a lengthened olub, mounted upon a 

 small tubercle closely outside the base of the velum. The cordyli are hollow, but their lumen is very 

 narrow, and in fully developed cordyli it is apparently always separated from the circular vessel, the 

 lumen of the peduncle being quite obliterated. -- This specimen seems to represent the fully developed 

 stage of growth, in so far as the tentacular bulbs are all of equal size, and the cordyli alternate with 

 the tentacles and are all situated on small tubercles. 



The velum is well developed but weak. 



As far as I am aware, this individual is the largest specimen of Ptychogcna lactea hitherto 

 described. In younger individuals there are a smaller number of lateral folds on the radial canals, and the 

 free edges of the lamellae carry a smaller number of papillae ; in specimens, less than about 35 ram in dia- 

 meter, the edges are quite smooth. In younger specimens the funnel-shaped extensions of the corners 

 of the stomach do not reach the distal ends of the gonadial part of the radial canals. The lateral 

 folds, which separate the dorsal part of the radial canal from the ventral part, are not developed in 



The Ingolf Expedition. V. 8. 5 



