272 ]\Tr. R. T. Giinther on the 



projecting into and ])avtly blocking up the lumen of the canal 

 (fig. 5). Hollow cavities often occur in this lobulated mass 

 of endoderm-cclls. 



As in Limnocodhim, the tentacles arc very numerous and 

 may amount to over two hundred in number. In some of the 

 smaller specimens the four ]nimary ]")erradial tentacles are 

 conspicuous on account of their greater length and thickness, 

 but in most of the larger examples they are almost equalled 

 in point of size by the interradial and even the adradial 

 tentacles, so that they are no longer readily recognizable. 

 Alternating with these primary, secondary, and tertiary series 

 tentacles of the fourth and even of the fifth and sixth orders 

 arise with great regularity, and it is only when the seventh 

 order of tentacles are intercalated that the typical regularity 

 of arrangement cannot be further traced. In preserved speci- 

 mens the relative length of the tentacles varies to a great 

 extent, indicating a considerable capability of contraction and 

 extension. The tentacles are hollow, the lumen of the 

 larger tentacles at any rate being clearly continuous with the 

 lumen of the ring-canal. The lumen of the tentacles is lined 

 with large, thin-walled, columnar endoderm-cells, which are 

 continuous with the endodermic lining of the ring-canal 

 (fig. 5). The transition from the tentacular endoderm-cells 

 to those of the ring- canal is very abrupt. The thread-cells are 

 of small size and generally arranged in little wart-like groups 

 or batteries (fig. 5), which are more or less disposed in whorls 

 and which are especially closely set at the tips of the tentacles. 



The proximal ends of the tentacles are all adnate to the 

 margin of the umbrella for some considerable distance 

 (figs. 4 and 5, te.), the older tentacles being adherent along a 

 greater length than the younger ones. At the points of 

 fusion the tentacles become partly imbedded in the substance 

 of the margin of the umbrella, wiiile the tentacular ectoderm 

 becomes continuous with that of the exumbrella, so that in a 

 section across the line of fusion an ectoderm lamella is seen 

 between the mesogloea of the tentacle and that of the 

 umbrella (fig. 5, ect.). 



On the side of the ring- canal opposite to that at which tlie 

 tentacles arise and just external to the origin of the velum is 

 situated a circle of sense-organs. These vary consider- 

 ably in number and are arranged at irregular intervals, so 

 that neither their number nor grouping can be brought into 

 relation with that of the tentacles. The structure of these 

 marginal bodies is peculiar. 



Iliey are refringent egg-shaped bodies attached to one side 

 of a round or ovate capsule, the walls of which are lined with 



