. Animal life as affected by the natural conditions of existence. Animal ecology. 192 THE INFLUENCE OF INANIMATE SUKEOUNDINGS. lungs, reopens the siphon, and admits a stream of water through it into the branchial ;" Some species of Kerilina of the Philippine and Pelew Islands live constantly on land, and apparently go into the water only when they want to lay their eggs; other species actually living in the water often make long journeys over land, as 1 myself have frequently had the opportunity of observing in the Pelew Islands. In these species the gills are comparatively sm
. Animal life as affected by the natural conditions of existence. Animal ecology. 192 THE INFLUENCE OF INANIMATE SUKEOUNDINGS. lungs, reopens the siphon, and admits a stream of water through it into the branchial ;" Some species of Kerilina of the Philippine and Pelew Islands live constantly on land, and apparently go into the water only when they want to lay their eggs; other species actually living in the water often make long journeys over land, as 1 myself have frequently had the opportunity of observing in the Pelew Islands. In these species the gills are comparatively small, and the roof of the branchial cavity is furnished with a dense vascular network of which the main branches unite in one large vessel; this is inserted in the heart—the auricle—and thus stands in precisely the tame relation to the lungs as the pulmonai'y vein of the true. Fig. 66.—Gecarcinus rusticota, a Land Crab. land-snails—Helicidce. Thiis the branchial cavity in this case seems to be capable of fulfilling not only its own proper func- tions, but also that of a lung. We know, moreover,"' that many species of crabs—Birguslatro, G'carcinus (fig. 56), Grapsoidea, Sesarma, and others—live far from all running or stagnant water in damp woods, under stones or decaj'ing trees, and are even able to expose themselves to the sun for hours. In most of these species true gills are present in the branchial cavity, but they fill at most a third or fourth of the space, and tlio cavities contain, besides water, a considerable quantity of air, as is shown by their constantly expelling air-bubbles at the sides. The supply of air thus driven out can of course be. 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 Semper, C. (Carl), 1832-1893. New York, D. Appleton
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