Sept.. 1893. THE LUCERNARIANS. 205 



send out swarms of ciliated embryos to go through the same strange 

 cycle of life. 



The second great division of the Hydrozoa, viz., the Hydro- 

 medusae, is, by most authorities, made to include both those fixed colonial- 

 living polyp forms, known generally as the Hydroid Zoophytes, 

 as well as the highly-specialised and complex floating siphonophores 

 exemplified by Physalia, the Portuguese man-o'-war. The former — 

 the Hydroid Zoophytes — which alone we need mention here, have a 

 life-cycle closely akin to that of the Scyphomedusae, the main differ- 

 ence being that the fixed stage — the hydriform — does not give origin 

 to medusae by transverse constriction, but, by oft-repeated budding, 

 produces usually large tree-like colonies. A medusiform sexual stage 

 is, however, present, though its importance is overshadowed and 

 masked by the great development of the hydriform. Thus such a 

 typical Zoophyte as Obelia gelatinosa forms, by repeated budding from a 

 ciliated embryo which has become fixed, a large colonial arborescent 

 community of many hydra-like and purely nutritive polyps. Later 

 on, certain modified organs produce, by budding, numerous tiny medusae, 

 which break loose, and float away as beautiful glassy, pulsating bells. 

 These differ from the medusae of the Scyphomedusae in having a 

 muscular membrane — vekmi — closing, all but for a central opening, 

 the mouth of the bell, hence the term " craspedote medusae." This 

 stage is sexual, and gives rise to free ciliated embryos. 



The Scyphomedusae have internal or gastral filaments, and their 

 hydriform stage is simple ; the Hydromedusas have no gastral fila- 

 ments, and their hydriform stage is colonial and frequently complex. 

 The Lucernarians possess the two former characters, and for these 

 and some less easily stated reasons, their intimate relationship with 

 typical Scyphomedusae is universally admitted. They, however, 

 differ from both divisions in that their life-cycle is not complicated. 

 The adult hydriform animal gives rise directly to ciliated embryos, 

 which settle down and become of the adult form without metamorphosis. 



Several species of Lucernarians are found in British seas. 

 The most common in the South (English Channel) is Haliclystus 

 octoradiatus, a most elegant, short-stalked, bell-shaped species found 

 almost invariably attached by an adhesive disc to blades of the sea- 

 grass [Zostera) close to low-water mark. The edge of the bell is 

 drawn out into eight points, each bearing a cluster of short clubbed 

 tentacles, well provided with stinging cells. Midway between each 

 twoi groups of tentacles is a hollow papilla, the " colleto-cystophore," 

 usually believed to be the equivalent or homologue of the tentacu- 

 locysts of the medusae. Normally, these are eight. A like number 

 of genital bands extend from the mouth into each of the marginal 

 points. In general outline Haliclystus resembles a shortly pedicelled 

 inverted cone with scolloped margin worked into eight projecting 

 tentacle-armed points. The size frequently reaches I in. in height, 

 by i^ in. across. 



