266 THE VOYAGE OF H.M.S. CHALLENGER. 



in 1841 near Zanzibar, and is the type specimen on which Milne-Edwards' description 



was based. 



The o-eneric diagnosis given by Mdne-Edwards is very descriptive and terse : — 

 " Polypieroide arborescent, dont I'axe est occupe par une cavite cylindrique commune, 

 au lieu d'une tige sclerobasique, comme si le tissu epithelique avait avorte." 



The natural relationship was, however, less happily indicated, inasmuch as the genus 

 was ranked along with Briareum, Solanderia, and Paragorgia under the Briaracese. 

 VerriU was the first to point out its relationship with Telesto} Hitherto only one species 

 — Ccelogorgia palmosa (Val.) {Lobularia palmosa, Yal.) — has been discovered, and its 

 distribution appears to be limited to the Mozambique Channel between Mozambique and 

 Zanzibar. 



Coelogorgia jiGblmosa (Val.) (PL XLIII. figs. 1-8). 



Lobtdaria palmosa, Val., MSS. Coll. du Mus. Jardin des Plantes, Paris. 



Ccelogorgia palmosa (Val.), Milne-Edwards, Hist. Nat. des Coralliaires, torn. i. p. 191; Hickson, 

 Phil. Trans, for 1883, p. 695. 



The colony consist of a stem which rises from a broadened base, attached by stolon- 

 like processes. The stem gives ofi", mainly on two sides, usually in alternate succession, 

 at obtuse or right angles, large branches or twigs. These may again bear twigs, or may 

 be beset with the club-shaped polyps which arise in spirals at wide intervals. The polyps 

 are not retractile ; their tentacles, furnished with spicules, lie down side by side over the 

 oral disc. The apex of the stem, like that of each branch, bears a terminal polyp, the 

 digestive cavity of which is continued as a tube of uniform width throughout the entire 

 stem. The wall of the main axis contains spicules, it tapers from the base to the apex, 

 and is penetrated by canals, which communicate by fine processes with one another. 

 From these canals the branch canals arise. These exhibit the same characters as those of 

 the main axis, and their cavities are never in direct connection with the inner cylinder 

 of the latter. From the canalicular network of the branches the polyps arise, which in 

 structure resemble the terminal polyp, but have but short digestive cavities. New 

 branches and polyps arise in similar manner as buds from the oesophageal portion of the 

 terminal polyps. In the formation of a branch the polyp bud grows in length and then 

 develops lateral polyps on its walls. The polyp bud, however, remains short with- 

 out forming lateral polyps. We may therefore, as in Telesto, regard the stems as 

 consisting of axial polyps of the first order, the branches of polyps of the second or the 

 third. The axial polyps appear, as far as the examination of the one colony is concerned, 

 to be sterile, whde the secondary polyps produce generative elements. There is there- 

 fore a sort of alternation of generations. The whole colony is rigid and brittle, only m 

 the twigs does it exhibit a slight elasticity. 



^ Mem. Boston Soc, vol i. p. 5, 1866. 



