BIGELOW: MEDUSAE AND SIPHONOPHORAE. 369 



the oral tentacles branch 5-7 times; the gonads are adradial; axial 

 ocelli are present. But the number of marginal tentacles per bundle 

 is greater in B. brittanica (16-30) than in B. niohc (8-15); and the 

 length of the basal trunk of the oral tentacles (proximal to the first 

 dichotomous branching) is much longer in the former than in the 

 latter. 



After actual comparison of specimens, I have not been able to find 

 any constant anatomical differences, other than such as are obviously 

 due to preservation or contraction or to different stages in development, 

 to separate B. niobe from B. fulva, and should not hesitate to unite 

 them, were it not for the occurrence of Medusa buds on the walls of 

 the manubrium in B. niobc, a phenomenon separating it not only from 

 B. fiilva, but from all known species of Bougainvillea. And so many 

 specimens of B. fulva have now been studied, over a range extending 

 across the whole breadth of the Pacific (Maas, 1905, Bigelow, 1909a), 

 and the Indian Ocean (Browne, 1916), that this type of asexual repro- 

 duction can hardly have Leen overlooked in them; whereas it is as 

 frequent in B. niobe (Mayer, 1910), as it is in Rathkea blumenbacliii 

 (Bigelow, 1909c; 1913; Hartlaub, 1911). Nor is this the only 

 Bougainvillea characterized by a peculiar reproductive cycle, B. 

 supcrciliaris carrying the planulae, resulting from its sexual reproduc- 

 tion, in the walls of the manubrium. 



An excellent account of the budding phase of B. niobe has been 

 given by Mayer (1910); and the present series affords an account of 

 the sexual phase, not previously recorded. 



Budding takes place in medium sized specimens, about 5-8 mm. in 

 diameter, a stage in which, as Mayer observed, there are about 8-10 

 marginal tentacles in each of the four groups, while the oral tentacles 

 branch 4-6 times. Budding specimens compose about one half the 

 present series; and there are almost as many larger specimens (8-10 

 mm. high) with gonads. The sexual organs are adradial, just as in 

 B. fulva (Maas, 1906a, fig. 10c), and B. brittanica (Hartlaub, 1911): 

 but the specimens are so contracted that I can not say whether they 

 are entirely discontinuous in the inter-, as the}' certainly are in the per- 

 radii, or whether they are occasionally joined, interradially, at the 

 upper end of the manubrium, as is the case in B. brittanica. In the 

 largest specimens there are 12-15 marginal tentacles in each bundle, 

 and the oral tentacles branch 7 or 8 times in several. But these organs 

 are so contracted, or intertwined, that in most cases it is impossible 

 to disentangle them. 



Most of the4arge specimens are so strongly contracted that the bell- 



