CLADONEMA RADIATUM. 357 



When Dnjardin wrote tlio nomenclature of tlic IIyuroida liad not yet acquired that definite- 

 ncss which subsequent investigations had conferred upon it, and the French zoologist designated 

 the trophosome of the present genus " Stauridie " {Staiiridium), while to the medusa which he 

 observed to be budded from his Stauridiiim he gave the name of Cladonema. 



Dnjardin observed not only the gemmation of the medusa from trophosome, l)ut he saw its 

 manubrium become loaded with eggs, which were afterwards deposited on the sides of his vase, 

 where they became developed into young /S'/a?«-«/«««-trophosomes. This is the first observation 

 by which the whole life series of a hydroid from trophosome to medusa by gemmation, and back 

 agoin by true generation to the trophosome, has been directly followed. 



The observations of Dujardin were afterwards confirmed and supplemented in some 

 important details by Krohn.^ 



Cladonema eadiatum, Dnjardin. 

 Plate XVII, figs. 1—10. 



Cladonem.\ RADIATUM (plaiioblast), — Dnjardin, in Ann. Sci. Nat., vol. x.'s, 1843, p. 370 j and 



vol. iv, 1845, p. 271, pis. xiv and xv. Krohn, 

 in Miiller's Archiv, 1853, p. 420, pi. xiii. 

 Gegenhaur, in Zeitschr. f. Wissensch. Zool., 

 vol. viii, 1857, p. 230. Van Beneden, Fauna 

 lit. de Belg., p. 159, pi. xii. Keferstein 

 and Elders, Zool. Beitr., p. 85, pi. xiii, fig. 5. 



Stauridie (trophosome), — Dnjardin, loc. cit. 



CoRYNE STAURIDIA (trophosome), Gosse, Devonshire Coast, p. 257, pi. xvi, figs. 1 — G. 



Cladonema radiatum, — Allman, in Ann. Nat. Hist, for May, 1864. Hincks, Brit. Hydr. 



Zoopb., p. 62, pi. xi. 



TROPHOSOME. — HroKOPHXTOX in the form of a very slender, creeping, ramified 

 filament, from which short, simple hydranth-bearing branches about one tenth of an 

 inch in height are given off at intervals, or presenting a free branching, slender stem, 

 which attains a height of half an inch or an inch ; peuisauc smooth. Htdeanth with 

 the tentacles of the proximal verticil much smaller than those of the distal. 



GONOSOME. — Planoblast (when mature) with the vertical and transverse 

 diameters of its umbrella nearly equal, and with a slightly prominent boss upon its 

 summit ; velum very wide, oral appendages, in the form of short cylindrical processes, 

 terminated each by two or three small spherical clusters of thread-cells, the marginal 

 tentacles with about four extensile branches nodidated with clusters of thread-cells, 



^ ' Miiller's Archiv,' 1853, p. 420, pi. xiii. 



