. Animal life as affected by the natural conditions of existence. Animal ecology. 218 THE INFLUENCE OF INANIMATE SUBKOUNDINGS. surroimckd, and thus enclosed, in the gall which gradually forms. It is not difficult to infer what the whole process must be from the different stages observable on one single mass of coral. A diseased excrescence is first produced by the young crab establishing itself between two branches, and the twig thus originating takes various forms according to the character of the species of coral. This is very conspicuous in the different specimens lying before me. In the Se
. Animal life as affected by the natural conditions of existence. Animal ecology. 218 THE INFLUENCE OF INANIMATE SUBKOUNDINGS. surroimckd, and thus enclosed, in the gall which gradually forms. It is not difficult to infer what the whole process must be from the different stages observable on one single mass of coral. A diseased excrescence is first produced by the young crab establishing itself between two branches, and the twig thus originating takes various forms according to the character of the species of coral. This is very conspicuous in the different specimens lying before me. In the Seriatopora, both the twigs are leaf-shaped and beset with more or less numerous offshoots terminating in sharp spines ; in the more solid Pocillopora the. Fig. e5.—Sld€fopora hyatrix, with galls inhabited by Hopalocarcinvs mi7-supialu. a a a, yoimg galls still half op*,'ii; b, an older one, closed, in which a close inspection may detect two opposite fissures. twigs also have spines, but they are more massive ; finally, in Sideropora, spines are wholly absent, and the two twigs between which the crab lives are altogether more massive. In the first instance the two leaf-like twigs are of course far apart, so that the crab could easily get in and out; but as it does not do this it is soon so surrounded by the growing together of the twigs, that it must remain a prisoner. The creature requires a con- stant and rapid renewal of the water in the gall in which it lives, for the purpose of lespiration; at first the Avater finds a free passage on all sides, but when the two twigs have bent over towards each otlier, the space through which it can find entrance and exit must gi-ow nariowcr and narrower. Moreover, from the structure exhibited by galls broken off from. 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 S
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