CORALS AND CORAL-ANIMALS. 197 



of being distinctly fringed or pinnate, have their upper surfaces minutely warted. Its polyparies 

 often form patches several yards in extent on the surface of the reefs ; one such patch is 

 included, although showing somewhat indistinctly, in the background towards the left of the 

 photographic reef-scape reproduced in Plate XIV. A coloured representative of a fully-expanded 

 polypary and of an enlarged polyp of this species, is delineated in Figs. 13 and 13A of Chromo 

 plate No. X. It is desirable to mention here that a decidedly lilac tint has been acci- 

 dentally substituted by the lithographic artist, for the typical pale porcelain-blue tint that 

 distinguishes the living organism. In another species of the warted-tentacled Xenia;, the polyps 

 and the common supporting stalk are a light stone-colour, and the minute tentacular warts and 

 the oral disk opaque white. This species, which is provisionally associated with the title of Xciiia 

 ochracea, is represented by Figs. 14 and 14A of the chromo plate last mentioned. 



A second group of the sheaf-shaped Alcyonaria, hitherto included in the genus Xenia, contains 

 those varieties in which the tentacles are distinctly pinnate. Among this series, one interesting 

 variety, obtained by the author at Warrior Island, Torres Strait, is remarkable, not only for the 

 size and delicate coloration of its polyps, but also for certain special physiological manifestations. 

 The expanded tentacles in this type measure over an inch in diameter. The colour of the stalks 

 and of the main shafts of the tentacles is a pale beryl-green, while the conspicuous tentacular 

 pinnae, and the substance of the common supporting polypary, are a pale ochreous-brown. The 

 special physiological phenomenon observed of this type was associated with the movements of its 

 tentacles. In all ordinary polyps, whether belonging to the coral-secreting or skeletonless sec- 

 tions, the component tentacles move quite independently of one another, and their action is either 

 irregularly vermiculate, or one of simple extension and retraction. In the present type, on the 

 contrary, all of the eight tentacles move synchronously, opening out and contracting in a con- 

 tinuous measured rhythm, averaging two seconds to each contraction. The action thus observed 

 was in all respects identical with the pulsating contractions of a jelly-fish, and was sug- 

 gestive of a less remote affinity between the Alcyonarian tribe and the medusiform Hydrozoa 

 than subsists between the last-named tribe and the coral-forming Madreporaria or skeletonless 

 Actinozoa. This suggestion of affinity receives substantial support from the fact that as 

 the radial processes throughout the jellv-fish tribe are invariably a multiple of four, and most 

 commonly eight, they thus correspond in number with the tentacular organs of an Alcyonarian, 

 while among the typical existing Madreporaria and Actinaria they are as mvariably a 

 multiple of six. In fact, were the outspread tentacles of a polyp of the pulsating Xenia, here 

 described, united by a transparent membrane, a jelly-fish or medusa-like organism would result, 

 so far as the general external features would be concerned. It not having been found possible 

 to identify this interesting type with any previously-described species, it is herewith associated 

 with the appropriate title of Xenia pulsitans Its polyparies, as shown in the coloured 

 illustration, Fig. 16 of Chromo plate X., embrace only a small number of associated 

 polyps. 



