. Elementary biology, animal and human. Biology. Fig. - Trichina in Muscle. (Leuckart.) the'umbo, in ever widening concentric rings, are the lines of growth of the animal, which indicate younger stages in its development. Let us now puU up a mussel and lay it on a sandy bottom. In a few moments the shell will open somewhat and from one end will project a pinkish body, which may finally extend some distance. This organ is the foot. If we watch long enough, we may see the mussel use the foot to push itself over the surface of the sand or it may burrow into the sand, and finally come to occ
. Elementary biology, animal and human. Biology. Fig. - Trichina in Muscle. (Leuckart.) the'umbo, in ever widening concentric rings, are the lines of growth of the animal, which indicate younger stages in its development. Let us now puU up a mussel and lay it on a sandy bottom. In a few moments the shell will open somewhat and from one end will project a pinkish body, which may finally extend some distance. This organ is the foot. If we watch long enough, we may see the mussel use the foot to push itself over the surface of the sand or it may burrow into the sand, and finally come to occupy a position like that in which we found it. Now if one is patient, and the animal feels at home, it wiU be pos- sible to see the method of eating and breathing. At the end oppo- site the foot there may sUghtly project from the shell a fringed and somewhat tubular-shaped structure. Let us place a little finely powdered carmine in the water above the opening. As the carmine slowly sinks and comes opposite the tube, the particles will suddenly be drawn into the tube. This shows that water is being sucked into the tube, and it brings with it oxygen and any food that may be near, such as mi- croscopic plants and animals. To learn any more about the feeding and breathing of the mussel it will be neces- sary to open the shell. Let us take an- other moUusk and pry open the valves. We shall soon find that this is not easy to do. evident after studying Figure 132. The valves are held together by strong muscles. So we pry the valves open a little with a heavy knife and then slip another sharp knife in close to the valve, where we meet an obstruction toward one end. When we have cut this, the valve opens at that exhalent siphon foot Fig. 131. — Mussel bur- rowing in sand. The reason will be. 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 perfect
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1912
