. Animal biology; Human biology. Parts II & III of First course in biology. Biology. ' FIG. 188. • ANODON, or fresh-water mussel. Lay the shells, fitted together, in your hand with the hinge side away from yon and tJie blunt end to tJie /<*/?( Fig. 188). Is the right or the left shell uppermost ? Which is the top, or dorsal, side ? Which is the front, or anterior, end ? Is the straight edge at the top or the bottom ? Our word " valve " is derived from a word meaning shell, because the Romans used shells for valves in pumps. Is the mussel a univalve or a bivalve ? Which kind is
. Animal biology; Human biology. Parts II & III of First course in biology. Biology. ' FIG. 188. • ANODON, or fresh-water mussel. Lay the shells, fitted together, in your hand with the hinge side away from yon and tJie blunt end to tJie /<*/?( Fig. 188). Is the right or the left shell uppermost ? Which is the top, or dorsal, side ? Which is the front, or anterior, end ? Is the straight edge at the top or the bottom ? Our word " valve " is derived from a word meaning shell, because the Romans used shells for valves in pumps. Is the mussel a univalve or a bivalve ? Which kind is the oyster ? The snail ? Does the mussel have bilateral symmetry ? Can you find a horny coveiing, or epidermis, over the limy shell of a fresh specimen ? Why is it necessary ? Does water dissolve lime ? Horn ? Find a bare spot. Does any of the shell appear to be missing there ? The bare projection on each shell is called the umbo. Is the umbo near the ventral or the dorsal line ? The posterior or anterior end ? Is the surface of the umbones worn ? Do the umbones rub against the sand as the mussel plows its way along ? How are the shells held together ? Where is the ligament attached ? (Fig. 189.) Is it opposite the um- bones or more to the front or rear? (Fig. 189.) Is the liga- ment of the same material as the shell? Is the ligament in a compressed condition when the shell is open or when it is closed ? (Fig. 189.) When is the muscle relaxed ?. FIG. 189. — DIAGRAM OF SHELL open and closed, showing mus- cle, m, and ligament, 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 Bailey, L. H. (Liberty Hyde), 1858-1954. New York, The Macmillan Co.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1910
