108 ATRACTYLID^E. 



Genus BOUGAINVILLIA, Lesson. 



Der. Named after a distinguished French voyager, Admiral Bougainville. 



HIPPOCRENE, Mertens, Mem. Acad. St. Petersbourg, 1835, 229. 

 MAIUJELIS, Steenstrup, Vidensk. Medel. for 1849-50, 43. 



GENERIC CHARACTER. Stem branched, rooted by a fili- 

 form stolon, the whole ccenosarc invested by a polypary ; 

 pohjpites fusiform, with a single wreath of filiform tentacles 

 round the base of a conical proboscis ; gonophores developed 

 from the branches and originating free zooids. 



Gonozooid : Umbrella (at the time of liberation] deep 

 bell-shaped ; manubrium shorter than the bell, with 4 oral 

 tentacles ; radiating canals 4 ; marginal tentacles 8, borne 

 in pairs on bulbs at the termination of the canals, with an 

 ocellus at the base of each. 



As the zooid advances towards maturity the tentacles of 

 the manubrium become branched, and those on the marginal 

 bulbs increase considerably in number. 



IT is a curious fact, and one that strikingly illustrates 

 the difficulty attendant upon the classification of the 

 Hydroida, that the sexual zooid of Corynopsis, one of the 

 Podocorynidce, is identical with that of the present genus, 

 at least in its earliest stage. 



The Margelis of Steenstrup has been adopted by 

 Agassiz for the members of Lesson's genus Bougainvillia, 

 which have " a long, slender digestive cavity, with but 

 slightly branching tentacles." But the differences be- 

 tween the two sections, which are confined to the repro- 

 ductive element, seem to me to be of slight significance, 

 and quite insufficient to justify the dismemberment of a 

 group that exhibits in its leading features so definite a 

 type of structure. 



