BRANCHIOCERIANTHUS IMPERATOR (aLLMAx). 237 



if possible, examine the original specimen of Monocaulus Imperator 

 in the British Musenm. To the results of his examination of the 

 specimens I shall return in the later part of this paper. 



Meanwhile an article was published in the Zoologischer An- 

 zeiger by O. Carlgrex (*99) throwing doubt on Mark's Brcmchio- 

 cerlanthus being an Actinian, and contending that it more 

 probably is a Corymorpha or at least a form standing very close 

 to Corymorpha. 



In June, 1801), a correction was published by Mark ('99) 

 himself in the Zoologischer Anzeiger. His previous preliminary 

 description had been based on external anatomy, and he now 

 frankly admitted that further researches had convinced him of the 

 fact that the animal in question must be more nearly related to 

 the Hydroidea than to the Actinia, though its exact affinities he 

 had not yet determined. In a postcript he mentions our conclu- 

 sions which had been communicated to him, as mentioned, by 

 letter, and thinks that both his and our specimens belong to the 

 same genus and that our specimen is probably identical with the 

 Monocaulus Imperator of Allman. 



Before going further I wish to express my deepest feeling 

 of obligation to Prof. Mitsukuri for the supervision and advice 

 which he has given during the progress of my work. 



Description. 



This hydroid is a solitary form consisting of a well marked 

 hydranth and a hydrocaulus. Its most striking feature is a 

 strongly expressed bilateral symmetry. The hydranth is disc- 

 shaped and bears two sets of tentacles and a circle of dendritic 

 gonosomes, all showing in their arrangement a well marked 



