. Essentials of biology presented in problems. Biology. 214 THE WORMS /fe i⢠around the body, and an inner set which runs the length of the body. The body is lengthened by the contraction of the cir- cular muscles. How might the body be shortened ? The under surface of the worm is provided with four double rows of tiny bristles called setae, every segment except the first three and the last being provided with setae. Each seta has attached to it small muscles, which turn the seta so it may point in the opposite direc- tion from which the worm is moving. If you watch a specimen carefully, you
. Essentials of biology presented in problems. Biology. 214 THE WORMS /fe i⢠around the body, and an inner set which runs the length of the body. The body is lengthened by the contraction of the cir- cular muscles. How might the body be shortened ? The under surface of the worm is provided with four double rows of tiny bristles called setae, every segment except the first three and the last being provided with setae. Each seta has attached to it small muscles, which turn the seta so it may point in the opposite direc- tion from which the worm is moving. If you watch a specimen carefully, you â will see that locomotion is accomplished by the thrusting forward of the anterior end; then a wave of muscular contraction passes down the body, thus shortening the body by drawing up the posterior end. The setae at the anterior end serve as anchors which prevent the body from slipping back- ward as the posterior end is drawn up. How the Worm digs Holes. â A feeding worm will show the proboscis, an extension of the upper lip which is used to push food into the mouth. Diagram to show how movement of a seta is accomplished; M, muscles; S, seta; W, body wall. (After Sedgwick and Wilson.). Forepart of an earthworm with the left body wall removed to show the body cavity and food tube within it: m, mouth ; p, pharynx, v, g, i, food tube. The earthworm is not provided with hard jaws or teeth. Yet it literally eats its way through the hardest soil. Inside the mouth opening is a part of the food tube called the pharynx. This is very muscular so that it can be extended and withdrawn by the worm. When applied to the surface of the soil, which is first moistened by the worm, it acts as a suction pump and draws it into the food tube. As the take organic matter out of the ground as food, they pass the earth through the body in order to. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appe
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
