[Illustration: FIG. 90.--SECTION OF AN ANEMONE _t_, tentacles; _m_, mouth; _s_, stomach; _b c_, body-cavity _p_, mesentery; _o_, egg-producing organ] The outer layer of the body-wall is provided with stinging cells which serve not only to protect the anemone from its enemies, but also to aid it in the capture of its prey, for which latter purpose they are distributed in much greater abundance in the tentacles. The body-cavity is divided into a number of communicating compartments by means of vertical partitions running from the body-wall and converging towards the centre of the cavity. These are called mesenteries, and are extensions of the inner layer of the body-wall. Five or six of these are larger than the others, extending from disc to base, and are called _primary mesenteries_. Between these are an equal number of smaller _secondary mesenteries_; and, sometimes, a third set of still smaller _tertiary mesenteries_. These internal partitions are best displayed in a transverse section of the body, which shows the double tube formed by the walls of the body and the stomach, together with the wheel-like arrangement of the mesenteries. At one time all animals that had a radial symmetry--the regular arrangement of parts round a common centre--were grouped together under the title of _Radiata_; but it has since been recognised that the creatures of this group exhibited such a great diversity of structure that they have been re-classified into two main divisions, one of which constitutes the cœlenterates which we are at present considering, and the other containing such creatures as star fishes and sea urchins. [Illustration: FIG. 91.--STINGING CELLS OF ANEMONE, HIGHLY MAGNIFIED _a_ and _c_, with thread protruded; _b_, with cell retracted] [Illustration: FIG. 92.--DIAGRAMMATIC TRANSVERSE SECTION OF AN ANEMONE _S_, stomach; _bc_, body-cavity; _m′_, _m″_, _m‴_, primary, secondary, and tertiary mesenteries] [Illustration: FIG. 93.--LARVA OF ANEMONE] On the surface of the mesenteries of the anemone may be seen the ovaries or egg-producing organs. These discharge the ova into the general body-cavity, after which they are ejected through the mouth. The embryos are minute jelly-like creatures that have an active existence, swimming about freely in the ocean by means of vibrating cilia, but after this period of activity they settle down and fix themselves, gradually assuming the adult form common to the species.