CLAVATELLA PROLIFERA. 385 



springing at intervals from the creeping filaments of the hydrorhiza. Htdranths 

 very much elongated, cylindrical in extension, with a dilated base, where they spring 

 from the summits of the rudimental hydrocaulus ; when fidly extended attaining a 

 height of about half an inch ; tentacles six to eight, with well-defined spherical 

 capitula. 



GONOSOME. — GoNOPnoRES in one or two clusters, each cluster containing two 

 or three gonophores, which are borne on a very short, branched peduncle which 

 springs from the dilated base of the hydranth. Planoblast dome-shaped, with its 

 margin continued into six short cylindrical tentacles, which divide, with their two 

 branches of nearly equal length, a little to the distal side of their middle point. 



Colour. — Hydranths wliite, tinged with a pale jjiiik at the distal extremity. jMedusaj with 

 pale reddish-yellow eiuloderni a])pcariiig through the translucent colourless ectoderm ; ocelli 

 red. 



Development of Gonosome. — Observed during the suamier and autunui. 



Habitat. — Attached to the sides of roek-pools. 



BaihymetricaJ Distribution. — Litoral zone near its upper limit. 



Localities. — Coast of Devonshire, Rev. T. Hincks and G. J. A. ; coasts of Cornwall, Cork, 

 and west of Scotland, G. J. A. ; Gulf of Genoa (free planoblast), Prof. Trinchesi ; Mediterranean 

 sea (free planoblast), Krohn, ]''ilippi (?). 



Among the observations which have of late years so greatly advanced our knowledge of the 

 Htdroida, one of the most important is that of Hincks, who, as already stated, found a hydroid 

 trophosome giving origin to gonophore-buds, having an intimate affinity with the free hydroid 

 organism described by Quatrefages, some years previously, under the name of Eleutheria diclio- 

 toma. This discovery renders it almost certain that Quatrefage's Eleutheria is also a planoblast, 

 originating as a bud from some hydroid trophosome, a fact which the excellent description 

 given by Quatrefages had already led more than one zoologist to suspect, but which, until 

 Hincks's discovery, had received no further confirmation. 



A free gonophore, apparently undistinguishable from that of Hincks's Clavatella prolifera, has 

 also been well studied by Krohn, who obtained it in the neighbourhood of Nice ; and by Fdippi, 

 who found what would seem to be the same organism in the marine aquariums of the Zoological 

 Museum of Turin ; while a nearly allied form, though apparently belonging to a different species, 

 has been examined by Claparede, who discovered it on the coast of Normandy.^ In none of 

 these, however, any more than in the original Eleutheria of Quatrefages, have the observers seen 

 the trophosome which has as yet been witnessed only by Hincks and by myself. For my first 

 opportunity of examining this remarkable little hydroid I am indebted to Mr. Hincks, who 

 directed me to the spot on the coast of Devonshire, where he originally discovered it. Since 

 then I have found the Clavatella in other localities, and have been enabled to make both tropho- 

 some and gonosome the subject of a careful study. (See above, p. 212.) 



' I am indebted to Professor Trinchesi, of the University of Genoa, for a drawing of the free 

 planoblast of a Clavatella, which is probably identical with the British species. 



