210 THE MEDUSAE. 



tentacles arise from large basal bulbs which are laterally compressed (PI. 42, 

 figs. 6, 11), and bear distinct spurs which curve over the exumbrella surface 

 of the bell margin (PI. 42, fig. 11). On the outer surface of each bulb is an 

 opening connecting the cavity of the tentacle with the exterior (PL 42, fig. 

 11 os.). At first I thought that these openings were accidental tears or 

 punctures ; but finding that they occurred on all the large tentacles, I pre- 

 pared several series of longitudinal sections of tentacular bulbs, the study 

 of which has convinced me that they are perfectly normal structures. Such 

 a section (PL 42, fig. 7) shows that at the margin of the opening the 

 ectoderm and endoderm are continuous, so that it does not present at all 

 the appearance of an accidental tear. So far as I can learn, such ostia have 

 not previously been described. 



Ocelli, — It is questionable whether the pigment spots in this species 

 can fairly be called ocelli, since they are clusters of separate granules 

 rather than discrete spots. They are present on the bases of the rudi- 

 mentary tentacles but absent from the large ones. In two tentacles of 

 intermediate size, in which very small openings have broken through in the 

 region of the spots, the pigment granules are scattered on either side of the 

 slit-like opening ; and it is possible that their absence from the large tenta- 

 cles is the result of such a scattering accompanying the further develop- 

 ment of the ostia. If this be true, then we might look forward to a stage 

 in which, with the growth of all the rudimentary into large tentacles, there 

 would be no pigment spots ; but from the advanced condition of the speci- 

 men I think it improbable that such a growth of all the rudimentary tentacles 

 would take place. 



Sense pits. — The ectodermal pits (PL 42, figs. 9, 10), to which, on account 

 of their resemblance to the sensory pits of many Acraspeda, I attribute a 

 sensory function, lie on the exumbrella surface, near the margin, usually one 

 just above the basal spur of each of the large tentacles (PL 42, fig. 6, s.). 

 Several tentacles, however, do not have them. Structurally they are simple 

 pits, lined with ectodermic bristle cells (PL 42, fig. 10). I have not been able 

 to find any similar organs described in any other Craspedotae. In many 

 Acraspeda, however, as is well known, similar pits occur, on the exumbrella 

 near the bases of the rhopalia, an example being figured in the present 

 memoir for Poralta rufescens ( PI. 13, figs. 4, 5). 



The manubrium is long; the lips folded and crenulated in an extremely 

 complex manner. The radial canals bear glandular diverticulae throughout 



