Fig. 2 represents, after Allman, a colony of Bougainvillea fruticosa of the natural size. It is a British species, which is found growing on buoys, floating timber, etc., and, says Allman, "When in health and vigour, offers a spectacle unsurpassed in interest by any other species--every branchlet crowned by its graceful hydranth, and budding with Medusae in all stages of development (Fig. 3), some still in the condition of minute buds, in which no trace of the definite Medusa-form can yet be detected; others, in which the outlines of the Medusa can be distinctly traced within the transparent ectotheque (external layer); others, again, just casting off this thin outer pellicle, and others completely freed from it, struggling with convulsive efforts to break loose from the colony, and finally launched forth in the full enjoyment of their freedom into the surrounding water. I know of no form in which so many of the characteristic features of a typical hydroid are more finely expressed than in this beautiful species." [Illustration: Fig. 3.--Bougainvillea fruticosa; magnified to show development.] Fig. 4 represents the Medusa or free form of this beautiful species. [Illustration: Fig. 4.--Bougainvillea fruticosa, Medusa-form.] If we pass to another great group of Zoophytes, that of the Jelly-fishes, we have a very similar case. For our first knowledge of the life-history of these Zoophytes we are indebted to the Norwegian naturalist Sars. Take, for instance, the common Jelly-fish (Medusa aurita) (Fig. 5) of our shores. The egg is a pear-shaped body (_1_), covered with fine hairs, by the aid of which it swims about, the broader end in front. After a while it attaches itself, not as might have been expected by the posterior but by the anterior extremity (_2_). The cilia then disappear, a mouth is formed at the free end, tentacles, first four (_3_), then eight, and at length as many as thirty (_4_), are formed, and the little creature resembles in essentials the freshwater polyp (Hydra) of our ponds. [Illustration: Fig. 5.--Medusa aurita, and progressive stages of development.]