7. Anthozoa (incl. Hydrocorallia). A. Zoantharia. 29 



bonate. By careful decalcification he obtained the organic matrix of the scale 

 and found it to be limited by a fine membrane, tending to give it the appearance 

 of a cell. But the calcareous scales are not the skeletons of calicoblasts, they 

 have not, morphologically, the value of cells, for nuclei are present only in very 

 few of them. In the ectoderm applied to the skeleton the skeletal elements 

 appear, each as a small mass of variable shape, with distinct fibrous structure, 

 its fibres lying parallel to each other and perpendicular to the surface of the 

 epithelium. This element, on one side of which is a small nucleus, calcifies 

 entirely when fully developed, it then ceases to form part of the still living 

 cell within which it developed and unites with the skeleton of which, hence- 

 forth, it forms a part, but its nucleus does not accompany it. The nucleus 

 withdraws into the living protoplasmic element and, after a period of rest, 

 it presides at the elaboration of a new skeletal element like the preceding 

 one. It is only after having assisted at the formation of a certain number of 

 these elements that the nucleus becomes enveloped in the last formed and is 

 then finally withdrawn from the living substance and incorporated into the 

 skeleton, in which it may still be recognised. On an average there are 150 

 scales without nuclei for every one with a nucleus. Each cellular area of the 

 calicoblastic layer, therefore, functions like a gland with rnerocrinal secretion 

 (agrees with von Koch, contrary to von Heider) but the secreted material is 

 elaborated entirely within the cell (as said by von Heider and contrary to von 

 Koch). - - See also M. Gordon. 



Jones discusses the growth forms of corals observed by him at Cocos- 

 Keeling and points out that even such a characteristic type of division as that 

 of the Meandrinae may be assumed by other corals e. g. an Astrcc-a, but when 

 this occurs it is usually a sign that the A. colony is not flourishing. The 

 thickness of the partition between two adjacent zooids and the amount of raising 

 above the surface of the individual corallites are subject to great variation which 

 affects the density and the surface pattern of the coral. All corals which possess 

 symbiotic alg tend to grow upwards (the zooids of Co<nopsammia willeyi and 

 nigrescens have their mouths turned down, they have no alg;u in their tissues, 

 they live in dark places, e. #., on the under sides of boulders) and all corals 

 tend to offer their greatest surfaces to the line of currents, for instance, vertical 

 plates offer their flat faces. Any coral which becomes established in rough 

 water tends to form a rounded or flattened mass, its structure is compact and 

 dense and its corallites tend to be flush with the general surface. Corals living 

 in smooth water are lightly calcified and delicately branched. Deep-water forms 

 are the most fragile, lateral branches are wanting and there is an absence of 

 pigment. On the upper surface of corals, which is exposed to the danger of 

 silting, the corallites tend to be small and raised from the general surface and 

 the intervening spaces are sculptured; on the lower surface the corallites are 

 larger, flush with the surface, and the intervening spaces are flat. The size 

 of the corallite and the amount of its projection from the surface are there- 

 fore not safe specific characters. Specimens of Pocillopora, from a floating tree 

 trunk which had been in the lagoon two years, showed varying growth forms 

 according to their position; those growing on its upper surface, over which, at 

 all states of the tide, waves broke were flattened bosses, those on its sloping 

 sides, which were in gently moving water, showed more tendency to branch, 

 and those on its lower surface, which were always in comparatively calm water, 

 were delicate branched forms. In a Madrepore, one of the main branches of 

 which was cleanly fractured, the apical zooid had, at the end of 100 days, 

 grown out 1 cm. and had budded from its sides 40 lateral daughter zooids and 



