S84 (JLAVATELLA PROLIFERA. 



with its tentacles in a single verticil, which surrounds the base of a conical 

 hypostoine. 



GONOSOME. — GoNOPiiORES developed in clusters on branched peduncles from the 

 body of the hydranth. Rudimental umbrella not fitted for natation. Manubrium 

 short, conical, destitute of oral appendages ; radiating canals six ; marginal tentacles 

 six, bifurcated, the outer branch of the bifurcation terminated by a capitulum of large 

 thread-cells, the inner by a claviform enlargement, which carries a suctorial disc of 

 attachment ; an ocellus at the root of each tentacle, but no distinct marginal bulbs. 



For the establisliment of the genus Chtvatella we are indebted to Hincks, who gave this 

 name to a hydroid trophosome, which he discovered on the south coast of England. From this 

 trophosome he observed tlie development of gonophores having a close resemblance to the free 

 medusiform body which had previously been described by Quatrefages under the name of 

 Eleuiheria dichotoma, but which had not been traced to a trophosome. Its chief difference from 

 mieutJieria consists in the fact that the inner branch of the marginal tentacle is terminated by an 

 apparatus for suctorial attachment, while in Eleufheria it ends in a capitulum of thread-cells like 

 that of the outer branch. 



This difference, however, I regard as of generic value, so that notwithstanding the close 

 resemblance between Quatrefages's EleufJieria and the gonophore of Clavatella, the two will 

 scarcely admit of being associated in a common genus, however closely the trophosomes may 

 ultimately be found to resemble one another. Clavatella and Eletdheria must, therefore, stand 

 as two distinct genera, though the latter will not admit of complete definition until the discovery 

 of its trophosome.^ 



Clavatella prolifera, EiiicJcs. 



Plate XVIII. 



Clavatella riiOLiFERA, — Hincks, \n Ann. Nat. Hist, for Feb., 18G], pis. vii and viii, 



Brit. Ilydr. Zooph., p. 73, pi. xii, figs. 2, 2a. AUma,n. 

 ill Brit. Assoc, Rep. for 1862, p. 100; and in Aun. Nat. 

 Hist, for May, 1S6L 

 Eleutheria (Plauoblast), — Krohn, in Wiegmanu's Archiv, 1861, p. 157, trans, in 



Ann. Nat. Hist, for Jan., 1862.' FUippi, in Mem. 

 della Reale Academia d. Scienze di Torino, ser. 

 ii, tome xxiii. 



TROPHOSOME. — Hydrocaulus consisting of very short cylindrical processes, 



' Elentlierhi, being as yet known only by its free planoblast is not included among the genera of 

 the descriptive part of the present monograph. 



