256 M. MIYAJIMA : 



e. The radial canal: — Mark mentions that the radial canals of 

 B. urceolus run *' from the base of the oral tube to the bases 

 of the marginal tentacles, before reaching which many of them 

 fork, each of the branches communicating with the lumen of a 

 single tentacle " (Makk '98, p- 150). The case is very dif- 

 ferent in our specimen in which (he radial canals do not 

 fork at all and do not communicate with the lumen of the 

 marginal tentacles. The latter, on the contrary, are the 

 continuations of the intercalated cords. 



Whether these differences are to be regarded as only 

 specific or due simply to the diöerences in size, age, etc., we 

 must leave for the present an open question. I am inclined, 

 however, to think that B. urceolus and our specimen are of 

 different species. 



References have already been made several times in the course 

 of the foregoing pages to the resemblance of our specimen to 

 Jlonocaulus imperator of Allman, a gigantic hydroid dredged 

 by the Challenger off Yokohama (stat. o27). The description 

 given by Allman of this animal in his report of the Hydroidea 

 of that Expedition Ç88) is not as exhaustive as is desir- 

 able. He makes no mention of any bilateral symmetry in the 

 animal, but we must remember that the specimens which he had 

 before him were extremely badly preserved, as he is careful to 

 mention, and that the figure of the animal wliich was made on the 

 spot by the artist of the Expendition must necessarily have been 

 made hurriedly, and as we can testify from our own observation of 

 the fresh object, it is very easy to overlook such a feature as bilateral 

 symmetry when the disc is lying in the midst of a mass of 

 tentacles. Of course the best thing we could do under the cir- 



