. The biology of the sea-shore. Marine biology. RESPIRATION IN SHORE ANIMALS 207 refresh themselves with a gulp of air. As a matter of fact, if the two fishes Boleophthalmus and Periophthalmus are prevented from reaching the surface in order to take in air they are drowned (Willey, 1911), a curious end for such typically aquatic forms as fish. In more or less similar fashion, the different common species of Littorina when placed in an aquarium will voluntarily climb up the sides to some distance above the water-level. They also die if permanently cut off from access to air. Many other amphibio
. The biology of the sea-shore. Marine biology. RESPIRATION IN SHORE ANIMALS 207 refresh themselves with a gulp of air. As a matter of fact, if the two fishes Boleophthalmus and Periophthalmus are prevented from reaching the surface in order to take in air they are drowned (Willey, 1911), a curious end for such typically aquatic forms as fish. In more or less similar fashion, the different common species of Littorina when placed in an aquarium will voluntarily climb up the sides to some distance above the water-level. They also die if permanently cut off from access to air. Many other amphibious snails occur outside. Fig. 14.—Periophthalmus, a tropical fish which moves about over mud flats at low tide by the aid of its pectoral fins. Note the modified pelvic fins acting as a sucker. our area. One of the most remarkable of these is Ampul- laria which has gill and lung cavities equally well developed and when living in water makes use of both in rapid alterna- tion (see Semper, op. cit.). Certain species of crabs exhibit an almost exact analogy with Amphibians proper, spending most of their time on land, and only returning to the water for very short intervals or perhaps only at breeding time. They owe their partial conquest of the land largely to the protected situation of their respiratory organs which prevents their becoming dried up, and partly also to the gradual accommodation to sub-aerial conditions which shore life affords. The begin- nings of air-breathing are already observable in the common crabs of our own sea-shore. But in order to see how far the process of emancipation from water-breathing may. 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 Flattely, Fredrick William, 1888-; Walton, Charles Livesey. New York, The Macmillan Company
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