BRANCHIOCERIANTHUS IMPERATOR (aLLMAN). 257 



cumstances was to appeal to the original specimens. At the 

 request of Prof. Mitsukuui, Prof. Mark, who was opportunely 

 staying in Europe at the time, was kind enough to examine the 

 type specimens of llonocaulus imper^ator, kept in the British 

 Museum. The results of his observation were not entirely conclu- 

 sive, as the specimens " have so long been in strong alcohol that it 

 was quite impossible to make out anything very satisfactorily." 

 He naturally made special efforts to ascertain the condition of 

 the hydranth — whether it was radially or bilaterally symmetrical. 

 In one specimen, he felt tolerably confident, though by no 

 means sure, that there was an interruption narrower than in 

 Branchiocerianthus u7'ceohis iîi the marginal tentacles. In another 

 specimen the central opening in the diaphragm which divides the 

 cavity of the hydranth from that of the hydrocaulus was found 

 much elongated — a point which in his opinion pointed to bila- 

 teral symmetry.'^' He also thought that there is much less ob- 

 liquity of the hypostomal region to the axis of the Hydroid than 

 in B. urceolus " for the wall of the hydranth between the con- 

 striction and the base of the tentacles can be seen to be nearly 

 the same height all around, or at least not markedly different on 

 opposite sides." This last point is against the view that our 

 specimen is identical with 3Ionocaulus imperator, for although 

 the disc is much less oblique in our specimen than in B. ur- 

 ceolus, as shown above, the hydrocaulus is attached at one end 

 of the sagittal (longitudinal) diameter of the disc. But Prof. 

 Mark adds, *' the specimens were so much wrinkled and folded 

 that I have not much confidence in this conclusion." There is 



* In our specimen the opening wliich puts the hydranth- cavity and that of the hydrocaulus 

 in communication is not elongated, but almost circular as already stated. 



