. A textbook in general zoology. Zoology. 82 EARTHWORMS, LEECHES, AND SEAWORMS of the waste materials of the body are excreted through the skin in the form of carbon dioxide. But the principal organs of excretion are convoluted tubes, known as ne- phridia, a pair of which is foxind in each segment of the body except the first three or four and the last one. Each ne- phridium opens at one end to the exterior by a minute pore in the body walls between the upper and lower rows of setae. The inner end of each nephridium has a funnel-shaped orifice lined with cilia that opens freely into the body c
. A textbook in general zoology. Zoology. 82 EARTHWORMS, LEECHES, AND SEAWORMS of the waste materials of the body are excreted through the skin in the form of carbon dioxide. But the principal organs of excretion are convoluted tubes, known as ne- phridia, a pair of which is foxind in each segment of the body except the first three or four and the last one. Each ne- phridium opens at one end to the exterior by a minute pore in the body walls between the upper and lower rows of setae. The inner end of each nephridium has a funnel-shaped orifice lined with cilia that opens freely into the body cavity. These organs act as simple kidneys and carry off the waste matters of the body. The nervous system. — This animal has a brain composed of two ganglia on the dorsal side of the anterior part of the pharynx. From each gangUon of the brain a nerve cord passes down- ward on the corresponding side of the pharynx. These cords meet below. Thus the pharynx is completely en- I, circled by what is called the " nerve ring," or "esophageal collar" (Fig. 42). After the nerve cords meet they 7"*'' /' .—H—'[~\~ff pass throughout the length of the g worm on the floor of the body cavity and become so closely fused that they Fig. 42.—ABterior end of appear as a single cord. In each seg- earthworm: b, brain; g, ment of the body both cords become ganglia. After Leuckart. , , , „ n i , t enlarged and form a double ganguon which appears as one. Smaller nerves pass from these ganglia to different parts of the body (Fig. 42). Senses of the earthworm. —It has been shown that all parts of the skin of the earthworm contain cells each of which gives off a nerve fiber that runs directly to the large. 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 Herrick, Glenn W. (Glenn Washington), 1870-196
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
