202 CORYDENDRIUM PARASITICUM. 



CORYDENDRIUM, Van Beneden. 

 Name. — From Kopmn\, a clul), and clvcpm; a tree ; in allusion to the form of the trophosome. 

 Sertularia, — Cavolini, Mem. Polyp. 



TROPHOSOME. — Hyduophyton consisting of a well-developed hydeocaulus, 

 and a creeping filiform hyduoriiiza ; the whole invested by a distinct perisarc. 

 Hydranths fusiform, with scattered filiform tentacles. 



GONOSOME. — Planoblasts borne on the hydrocaulus. Form of medusa 

 unknown. 



The present genus was instituted by Van Beneden for the Sertularia parasitica of Cavolini, 

 a hydroid which Ehrenberg had incorrectly referred to his genus Syncoryne ; Agassiz, believing 

 that the species of Cordyloplwra are congeneric with Cavolini's hydroid, refers them both to the 

 genus Syncoryne, which, however, he iinds it necessary to reconstruct for their admission. I have 

 already shown that this view is untenable. 



*^* CORYDENDRIUM PARASITICUM, CavoUni. 



Sertularia parasitica, — Ciwolini, Mem. Polyp., Sprengel's translation, p. 83, tab. vi, figs. 



8—13. 

 Syncoryne parasitica, — Ehrenberg, Corallenthicre, Abhandl. der Akad. Wisseus., Berlin, for 



1832, p. 295. Agassiz, Coutr. Nat. Hist. U.S., 



vol. iv, p. 339. 

 CORYDENDRIUM PARAS1TICU3I, — Vtiii Beiicchn, BuI. Ac. Hoy. de Bruxellcs, 1844, p. 313. 



TROPHOSOME. — Hydrocaulus attaining a height of about two inches; much 

 branched ; fascicled^ in the main stems, single in the smaller ramuli. Hydranths 

 with a very extensile and dilatable hypostome. 



GONOSOME. — GoNOPiiORES on short peduncles, springing singly from a point 

 close to the junction of the ultimate ramuli with the branches from which they arise. 



General colour. — Dark red. 



^ T use the term " fascicled '' here and elsewhere to indicate a composition out of many 

 longitudinally colierent tubes, each invested by its own perisai'c. 



