364 THE LIVING ANIMALS OF THE WORLD 



in a condition of healthy growth, yielding a spectacular effect that vies with that of any 

 floral parterre. Sometimes large areas, acres upon acres in extent, may be covered with one 

 almost uniform purple, green, brown, or other coloured growth of the branching stag's-horn 

 species. The aspect presented is not unlike that of a heath-covered common. 



In addition to the solid, calcareous-skeletoned Madrepores, or " Stony Corals," as they are 

 often termed, there are a number of species in which a skeleton composed only of loosely 



aggregated calcareous spicules 

 is produced. The so-called 

 FI.K.XIHI.K. CORALS, or Si:\- 

 l-ANS, belong to this category, 

 as also the precious CORAL 

 <>K C"MMi:ui i:. In the last- 

 named species the solid, 

 brilliantly coloured skeleton 

 so much prized as an article 

 of jewellery is deposited . 

 supplementary basis outside 

 the tissues by which the star- 

 patterned skeletons of the 

 stony corals are secreted. 



A group which demands 

 brief notice is that of the 



HYDROID Po| M'S. These 



include the majority of the 

 JK.I.I.V-KISMK.S, a few coral- 

 secreting species, and tin- 

 ganisms whose seaweed-like 

 horny skeletons, known as Si A- 

 1 IRS, are, in common with tin e 

 of Sea-nuts, included among 

 the flotsam and jetsam on 

 ' \ cry - .1 lieach. In the 

 COMMON HYDRA, or FRI-II- 

 \VATK.K Poi.Yl', an exceptional 

 fresh-water representative of 

 this group is presented. It may be likened to a tiny sea-anemone, having, when extended, 

 a slender foot-stalk and long thread-like tentacles. Like a sea-anemone, it will shrink up 

 when disturbed into a mere button of jelly. Its organisation is more simple than that of 

 the anemone, its body-cavity being a simple sac, without any intucking of the "orifice, or 

 strengthening by supplementary membranous partition-. A similar >mipL- structural plan 

 is characteristic of all the organisms belonging to the series. An interesting phenomenon 

 connected with the fresh-water hydra is the circumstance, demonstrated now over a century 

 ago, that, if one of these animals be cut up into little pieces, each separate fragment is 

 capable of repairing itself and growing into a new polyp. 



The jEU.Y-Hsin 5, or Mi IH-A-, and their allies would appear at first sight to possess but 

 little structurally in common with the Coral-polyps and Sea-anemones. In their most familiar 

 form they are represented by a more or less translucent boll haped body, which drifts with 

 the current or propels itself through the water by its alternate expansions and contractions. In 

 the centre of the lower surface, occupying the position of the bell's clapper, a polyp-like, 

 tubular mouth is usually discernible, ami this is frequently surrounded by a circle of tentacles, 

 sometimes simple and sometimes elaborately ramified. Long, thread-like tentacles are also 

 commonly developed around the margin of the swimming-bell. 



&. 



CySd 



f>ut,h If. Snllh-Kinl, F.Z.S.] 



A QUEENSLAND STAR-CORAL 



Tkit tfefiet in life it of a pale lemon-yellow tint 



