31:2 BOUGAINVILLIA RAMOS A. 



TROPHOSOME. — IIydhocatjlus attaining a height of from one to three inches, 

 much hranched, tlie ultimate branches for the most part alternate ; main stem and 

 principal branches fascicled towards the base ; perisarc with shallow annulations 

 at tlie origin of the branches. Htdranths with about twelve tentacles, which in 

 extension are usually carried nearly straight, with every alternate one elevated or 

 depressed ; perisarc continued over the body of the hydranth as far as the roots of 

 the tentacles, in the form of a cup-like extension, into which the hydranth, in extreme 

 contraction, may be almost completely withdrawn. 



GONOSOME. — GoNOPHORES on moderately long peduncles, which spring from tlie 

 ultimate ramuli, on which they occur either singly or in sub-vcrticillate groups of two, 

 three, or more. 



Colour. — Body of hydrantli with manubrium and marginal bulbs of medusa pale pink, 

 ocelli carmine, perisarc of liydrocaulus straw-colour. 



Develojjment of Gonosome. — Autumn. 



Habitat. — Attached to rocks near low-water mark, and to other liydroids and old shells from 

 the coralline and deep-sea zones. 



Baflii/metrical disirihution. — Laminarian to deep-sea zones. 



Localities. — Coast of Belgium, Van Beneden ; Firth of Forth, Dr. S. Wright ; Oban, Argyle- 

 shirc, Rev. T. Hincks ; south coast of Devonshire, Rev. T. Hincks and G. J. A. ; coast of 

 Northumberland, Mr. Alder. 



Bougainvillia ramosa, in its complete form, presenting both trophosome and gonosome, was 

 first described by Van Beneden, who, believing it to be identical with the Eudendriiim ramosum of 

 Ehrenberg, assigned to it this name. Ehrenberg's Eudendrium ramosum, however, is an entirely 

 different hydroid, being identical with the Tuhularia ramosa of Linnaeus, the " small, ramified, 

 tubular coralline " of Ellis. We now know, as has been just said, that the adult medusa of 

 Vail Beneden's Eudendrium ramosum is either the Bouffaijivillia Britannica of Forbes or a closely 

 allied form. Were we sure of its identity with Forbes's medusa, the law of priority would 

 compel us to assign to Van Beneden's hydroid, not only the generic name of BoiigainviUia, Imt 

 the specific name of Britannica. In the absence, however, of absolute proof of this specific 

 identity it will be wiser to retain Van Beneden's specific name of ramosa, wdio, moreover, was the 

 first to give a good drawing and description of the species. 



BoiigainviUia ramosa forms profusely ramified tree-like growths on the various bodies to 

 which it attaches itself, and in the confinement of our arpiaria will continue for many days to 

 throw ofi" successive crops of medusa;. The medusa, immediately on liberation, darts away through 

 the surrounding water, the marginal tentacles being at the same time contracted and thrown 

 back upon the umbrella in the form of short, thick, curved, somewhat clul>shaped appendages. 

 When it comes to rest the tentacles are extended, and when the medusa is floating passively on 

 the water they are stretched out for some distance nearly horizontally, and for the rest of their 

 length hang down vertically in the water. 



I have not succeeded in getting the young medusae to undergo in confinement the changes 



