246 HYDROID^. Part IV. 



side of the disk upon which the tentacle is attached (PI. XXV. Figs. 14 and 14% n) 

 is a little larger than the rest of the bell, and, on this account, the medusa appears 

 asymmetrical and gibbous, and hence its name.^ 



The base {Figs. 14 and 15, J^) of the tentacle is broadly triangular, and quite 

 thick, but varies in this latter respect when its cavity is more or less distended with 

 the circulating fluid. Beyond the swollen, triangular portion, the tentacle is solid, 

 and covered by a layer of coarse, loose cells, which appear as distinct groups, in 

 rings, when the tentacle is extended {Fig. 15, g^). The length of the tentacle 

 varies from twice to three times the length of the bell. There are times when 

 the hollow base stretches until it is two thirds as long as the height of the disk 

 {Figs. 15 and 15% g), and then it may be distinguished from the solid portion {g^) 

 by the absence of the transverse rings of cells. At first sight the base of the 

 tentacle may seem to be manifoldly lobed {Figs. 14, 14% and 15,//^) on the inner 

 side ; but closer inspection reveals the true nature of these seeming lobes. They 

 are, in reality, medusas, in various stages of development, the oldest of which seem 

 to be identical with the one from which they bud. 



There are five orange-red, granular bands {Figs. 15 and 15" k k^ k^ k^ k^), about 

 as broad as the radiating canals, which extend from the base of the disk to, or 

 near, its apex, on its exterior surface ; two of them, starting from a broad, triangular 

 base {Figs. 15 and 15% k^ P), suddenly narrow, and pass upwards, one on each 

 side of the radiating canal which leads to the tentacle, and gradually converge 

 in the direction of the apex {Fig. 15% k*); the other three having a similar basis 

 {k^), opposite the point of junction of the circular and radiating canals, pass upward, 

 each one over a radiating canal {Figs. 15 and 15% P) towards the apex, or, more 

 correctly, to points opposite the junction of the canals with the digestive cavity 

 {d). At the latter end of the breeding season in April, these bands were not 

 so conspicuous as to attract attention, and, therefore, were not represented in the 

 figures {Figs. 14 and 14") made at that time, and if they were really present, 

 they have been mistaken for mere wrinkles in the epidermis. Early in the season 

 they are so strongly marked as to be seen by the naked eye, although the 

 medusa is not larger than yV of an inch in diameter. The difference in the 

 season may also account for the fact that the later medusse {Figs. 14 and 14*) 

 have so few, and so imperfectly developed buds, whilst on the earlier ones {Figs. 15 

 and 15'') the young (/) are more numerous, and have quite long tentacles (/^). 



The close resemblance of our medusa to those described by Forbes as Steen- 

 strupia and Euphysa leaves no doubt in my mind that these two genera are founded 

 upon the free brood of some of the European species of the genus Tubularia, 



' v^oi, hump, y.dSbJV, a bell ; Iljbocoilon. 



