BKANCHIOCERIAMTHUS IMPERATOll (ALLMAN). 253 



mon cavity outwards and downwards. These canals, though not 

 visible from the surface, may be regarded as corresponding to the 

 radial canals in our specimen, since they both arise from the 

 upper cavity of the hydranth and are arranged alternately with 

 the marginal tentacles. 



o. The tentacles are filiform and arranged in two sets, oral 

 (distal) and marginal (proximal), as is characteristic of the 

 tentacles of Tubularidœ, Oorymorphidœ^ and 3Ionocaulidm. The 

 cavity of the tentacle is mostly obliterated, being filled up with 

 a cellular tissue — a condition very frequently met with in the 

 tentacle of the Hydrozoa. 



4. The dendritic appendage is a true gonosome which bears 

 in its summit the sexual elements. Our specimen seems to be 

 immature, hence it could not be decided whether the gonophore 

 is a planoblast or a sporosac. 



5. The hydrocaulus is marked with many wavy bands visible 

 from the surface, and possesses a thin sheath with filamentous 

 appendages at its lowest end. 



Considerations on the Systematic Position of our 

 Specimen. 



Those who would compare the account given above of the 

 structure of our specimen with that of Branchiocerianthus urceolus, 

 Mark ('98) will not for a moment doubt that we have in these 

 two cases essentially similarly constituted animals. It seems almost 

 superfluous to call attention to the points of likeness : the hydro- 

 caulus with the wavy bands in its upper half and with the sheath 

 and filamentous appendages at its base, the hydranth surmounting 

 the hydrocaulus, with its radial canals, dendritic gonosomes, and 

 two sets of tentacles, all of which show a strongly expressed 



