. A manual of zoology. Zoology. GENERAL ORGANOLOGY. 1U7 though mot so great, are the differences between carnivorous and plant-eating beetles. II. Respiratory Organs. Sources of the Oxygen used in Breathing.—The oxygen which each animal must obtain in exchange for the carbon dioxide formed in the tissues is derived either from the air or from tlie water, according as the animal is terrestrial or aquatic. Less frequently it is the case that water-dwellers breathe air, and hence are com- pelled, from time to time, to rise to the surface of the water for a. Fig 61 —Left second foot of a crayfish
. A manual of zoology. Zoology. GENERAL ORGANOLOGY. 1U7 though mot so great, are the differences between carnivorous and plant-eating beetles. II. Respiratory Organs. Sources of the Oxygen used in Breathing.—The oxygen which each animal must obtain in exchange for the carbon dioxide formed in the tissues is derived either from the air or from tlie water, according as the animal is terrestrial or aquatic. Less frequently it is the case that water-dwellers breathe air, and hence are com- pelled, from time to time, to rise to the surface of the water for a. Fig 61 —Left second foot of a crayfish with attached gill ('ir). (After ; (xp, cox'oDodite- dp, basipodite; ip, isohiopodite; mp, meropodite; cp, carpopodite; pi>, propodite; dp, dactylopodite; , bristles of the coxopodite; c, lamina of the gill. supply of air; this is true for the great marine mammals, and for many insects, spiders, and snails which are found in fresh water. Air- and water-breathing takes place exclusively through the skin, so lonty as this is delicate and readily permeable, and so long as no hio-her development of organization necessitates a more active intercliange of material. If, on the other hand, the demand for oxvo-en be greater, other more special breathing-organs are found Vfpg for water-breathing, lungs and trachea for air-breathing, in. 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 Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1902
