358 CLADONEMA RADIATUM. 



and terminated each by a spherical cluster larger than those which are borne along 

 their length ; the sucker-bearing appendages, usually three in number, smooth. 



Colour. — Body of hydranth very pale reddish ; perisarc light yellowish brown ; manubrium 

 of medusa very pale reddish, marginal tentacles and their branches crimson brown ; ocellus deep 

 crimson. 



Development of Gonosome. — Spring and summer. 



Habitat. — Attached to stones, &c., in the sea. 



Bathymetrical distribution. — Unknown, probably confined to the litoral zone. 



Localities. — Northern shores of France, Dujardin ; Coast of Belgium, Van Beneden ; 

 Coast of Devonshire, Mr. Gosse; Coast of Kent, Mr. Dovvker; Messina, Krohn, Gegenbaur, 

 Kefferstein and Ehlers. 



I take for granted that the synonymy given above refers to one and the same species, namely, 

 the original Cladonema radiatum of Dujardin, because, though some slight differences may be 

 noticed between the descriptions, these do not appear to be sufficiently marked to justify ovu" 

 regarding them as of specific value. In some cases they are certainly the results of mere 

 differences of age. 



Though the medusa of the present species has been occasionally met with in the open sea, 

 the trophosome has as yet been found only in the confinement of tanks appropriated to the 

 preservation of living marine animals, and in all those cases it has shown itself spontaneously 

 without any attempt being made to introduce it. Whether the form of the trophosome has 

 undergone any change in consequence of the artificial conditions to which it has been thus 

 exposed it is impossible to say. It presents itself, at all events, under two modifications ; in one 

 the hydrophyton runs over the supporting surface as a very slender branching filament, from 

 which equally slender simple branches, about one tenth of an inch in height, are given oft' at 

 intervals, each carrying a hydrantli ; in the other form (that represented in the plate) there is a 

 free branching, slender stem, which attains a height of from half an inch to an inch. 



Since Dujardin the principal original observers of this hydroid have been Mr. Holdsworth 

 and Mr. Hineks in this country (see Hincks, loc. cit.), and M. Van Beneden on the Continent. 

 Some years ago I obtained specimens of the trophosome from one of the tanks belonging to the 

 zoological survey of London, in which it had appeared in abundance, but no planoblasts were 

 developed from them. I am indebted, however, to Mr. Dowker, of Stourmouth House, Kent, 

 for living specimens of Cladonema radiatum, presenting both trophosome and gonosome. They 

 showed themselves in a large tank filled with water from the neighbouring coast, and have 

 afforded me an opportunity of making a careful study of this remarkable hydroid (see above, 

 page 216). 



There can be little doubt that Van Beneden is right in regarding a medusa, which made its 

 appearance in an aquarium supplied with water from the coast of Belgium, as the medusa to 

 which Dujardin gives the name oi Cladonema ; but it is not easy to say why he could have 

 thought himself justified in referring it to a naked //y^/rrtc/iw/a-like trophosome, which he noticed 

 at the same time in his aquarium.' In favour of this association there are not the slightest 



' 'Faun. lit. de Bclgique,' p. 110. 



