326 PORPEMA PRUNELLA. 



in several particulars better material allows correction and emendation of his 

 observations. 



In general outline the largest specimens are rather higher than his, height 

 and breadth, leaving out of account the central gastrozooid, being about equal, 

 whereas his figures are almost twice as broad as high; but the fact that 

 his description was based entirely on contracted alcoholic material, makes it 

 imsafe to lay stress on this apparent difference. It may be a concomitant of 

 different stages in growth. 



Adult individuals of P. globosa (= P. medusa), according to his figures, 

 agree in height with the "Albatross" specimens. The tentacles, as already 

 pointed out, are distributed evenly over the tentacular zone, not in groups. 



Haeckel ('88b, pi. 48, fig. 4) represented the limbus as radially lobed, 

 instead of entire, as it is in the "Albatross" specimens and in Porpita. But 

 since he has himself shown it entire in two other views ('88b, pi. 48, fig. 1,2), 

 and since it is often artificially split radially in alcoholic material, the apparent 

 lobes were probably the result of mutilation. Indeed, although he states in 

 his diagnosis of the genus that the margin is lobed, in his account of the "limbus 

 umbrellae" of this species he fails to mention any such appearance. As shown 

 by Haeckel, the limbus is proportionately very much broader than it is in Por- 

 pita, and the palial canal system much less complex. In his view of the upper 

 surface ('88b, pi. 48, fig. 4) he shows fifteen broad radial canals near the centre, 

 connected with one another by a ring canal, and branching irregularly so that 

 at the margin of the limbus there are forty-one. In one of the present speci- 

 mens there are fourteen canals near the centre of the disc, and forty-five at the 

 margin (Plate 26, fig. 3). The entoderm of the canals, especially near the outer 

 end in the region of the limbus, sends out numerous amoeboid processes, simple 

 and branched, just as happeuvS in the canals of the limbus in Porpita. At the 

 margin of the limbus, the radial canals are connected by a circular canal, but 

 so crowded are the marginal muciparous glands that it is only on sections that 

 this canal can be distinguished. Each radial canal branches at the zone of 

 junction of limbus and pneumatophore, one branch running into the limbus, 

 the other running downward into the tentacular zone as will be described later. 



Pneumatocyst. In the specimens sectioned, there were from 12-15 circular 

 chambers, besides the central chamber. There are no radial chambers; but, 

 as is seen in the cross sections, the outer wall of the central chamber is folded 

 so as to form eight vertical pockets (Plate 26, fig. 4). Haeckel states that 

 the central chamber is surrounded by eight radial chambers; but his figures 



