. A manual of zoology. PHYLUM CCELENTERATA surface of the theca a number of radiating partitions, the septa, proceed inwards or towards the axis of the cup, some of them meeting in the middle to form an irregular central mass or columella, which in some kinds of corals forms an independent, pillar-like structure arising from the middle of the base. In the living condition the polype fills the whole interior of the corallite, and projects beyond its edge to a greater or less degree according to its state of expan- sion. The septa alternate with the mesenteries, each being in- vested by an in-tu
. A manual of zoology. PHYLUM CCELENTERATA surface of the theca a number of radiating partitions, the septa, proceed inwards or towards the axis of the cup, some of them meeting in the middle to form an irregular central mass or columella, which in some kinds of corals forms an independent, pillar-like structure arising from the middle of the base. In the living condition the polype fills the whole interior of the corallite, and projects beyond its edge to a greater or less degree according to its state of expan- sion. The septa alternate with the mesenteries, each being in- vested by an in-turned portion of the body-wall; so that, though having at first sight the appear- ance of being internal structures, they are really external, lying alto- gether outside the enteric cavity, and are in contact throughout with the ectoderm. The almost infinite variety in form of the compound corals is Fig. 60. — Pennatula sulcata. Entire colony. Natural size, due, in the main, tO the Various I, lateral branch. (After ' Koelliker.) methods of budding. According to the mode of budding, massive corals are produced in which the corallites are in close contact with one another, as in Astrcea (Fig. 62) ; or tree-like forms, such as Den- drophyllia (Fig. 63, A), in which a common calcareous stem, the coenenchyma, is formed by calcification of the coenosarc,1 and gives origin to the individual corallites. 1 See p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, T. Jeffery (Thomas Jeffery), 1850-1897; Haswell, William A. (William Aitcheson), 1854-1925. New York, The Macmillan Company; London, Macmillan & Co. ,Ltd.
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