CORDYLOPHORA. 251 



The description and figure of Ithixogelon fimforiim given by Agassiz arc those of male speci- 

 mens only, but Prof. 11. J. Clarke, who had an opportunity of observing both sexes, has described 

 and figured female colonies, lie has noticed that the ova, after the earlier stages of their 

 development have been passed in the interior of the gonophore, break through its walls, and 

 then remain for some time confined between the outer ectodermal layer of the gonophore and its 

 perisarcal investment. 



Agassiz, from whose descriptions I have selected the characters out of which the diagnosis 

 just given has been constructed, informs us that the male gonophore becomes converted into a 

 hydranth after the discharge of its contents. This converting of a gonophore into a hydranth 

 has been already referred to in the former part of the present monograph,^ where it is I'cgardcd 

 as an abnormal phenomenon. 



COEDYLOPHOEA, Allnian. 



Name. — From /copSuXij, a club, and <popUo, I bear ; in allusion to the form of the trophosome. 



Syncoryne, — Agassis. 

 (?) TuBULARiA, — Affard/i. 



TROPHOSOME. — Htdrophyton consisting of a well-developed ramified htdeo- 

 CAULTJS, which springs from a creeping filiform HTDEOimiZA ; the whole invested by a 

 PEEiSARC. Htdranths fusiform. 



GONOSOME. — Sporosacs borne on the hydrocaulus. 



The genus Cordylophora was instituted by me many years ago " for a tubularian hydroid 

 singularly exceptional in its mode of life, for it was found in fresh water, and thus along with one 

 other genus, namely. Hydra, affords an exception to the otherwise universally marine habitat of 

 the Hydroida, 



Agassiz,' believing that the hydroid on which I founded the genus Cordylophora is congeneric 

 with a hydroid discovered long ago by Cavolini in the Bay of Naples, and described by him under 

 the name of Sertdaria parasitica, would refer them both to the genus Syncoryne of Ehrenberg. 



From this determination, however, I must altogether dissent. The name of Syncoryne was 

 introduced by Ehrenberg in 1833* in order that it might replace that of Stijmla, Sars' name for 

 a genus of hydroids exactly equivalent with the Coryne of Gartner. To this genus Syncoryne 



^ See above, p. 204.. 



* ' Reports of the Meeting of the British Association,' held in Cork, 1843, and ' Ann. Nat. Hist.,' 

 xiii, p. 330. 



' ' Contr. Nat. Hist. U.S./ p. 239. * ' Corallenthiere des llothes Meeres.' 



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