. Beginners' Zoology . .What advan-tage in * Are the gills smoothor wrinkled .-* (Fig. 215.) What ad-vantage? The bony supports ofthe gills, called the gill arches, areshown in Fig 216. How manyarches on each side ? The gill arches have projectionson their front sides, called gill rakers, to prevent food from being washedthrough the cleftsbetween the fringes on therear of the gillarches are calledthe gill filaments(Fig. 216). Thesefilaments supportthe thin and much-wrinkled borders ofthe gills, for thegills are constructedon the plan of exposing the greatest possible surface t
. Beginners' Zoology . .What advan-tage in * Are the gills smoothor wrinkled .-* (Fig. 215.) What ad-vantage? The bony supports ofthe gills, called the gill arches, areshown in Fig 216. How manyarches on each side ? The gill arches have projectionson their front sides, called gill rakers, to prevent food from being washedthrough the cleftsbetween the fringes on therear of the gillarches are calledthe gill filaments(Fig. 216). Thesefilaments supportthe thin and much-wrinkled borders ofthe gills, for thegills are constructedon the plan of exposing the greatest possible surface tothe water. Compare the plan of the gills and that of thehuman lungs. The gill opening on each side is guarded byseven rays (Fig. 216) along the hinder border of the. Fig. 216. —Skeleton around Throat of Fish ii6 BEGINNERS ZOOLOGY gill cover. These rays grow from the tongue bone. (Fig. 216. This is a rear view.)Watch a live fish and determine how the water is forced between the gills. Is the mouth opened and closed in theact of breathing ? Are the openings behindthe gill covers opened and closed ? How
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