. Elements of zoology, to accompany the field and laboratory study of animals. Zoology. Fig. 226. â The scal- lop (Pectcn irra- dians). Right or lower vah'o. One- half nat. size. shaped shells attach in clusters or beds to rocks near low tide. In the absence of rocks they may attach themselves to the roots of the marsh-grass. They form so solid a wall here as to protect the mud and the marsh-grass that is growing in it from being washed away. Thus the relations of marsh-grass and mus- sels are reciprocally advantageous (Fig. 225). Mussels are etlible and in Europe thej^ are reared for the mark
. Elements of zoology, to accompany the field and laboratory study of animals. Zoology. Fig. 226. â The scal- lop (Pectcn irra- dians). Right or lower vah'o. One- half nat. size. shaped shells attach in clusters or beds to rocks near low tide. In the absence of rocks they may attach themselves to the roots of the marsh-grass. They form so solid a wall here as to protect the mud and the marsh-grass that is growing in it from being washed away. Thus the relations of marsh-grass and mus- sels are reciprocally advantageous (Fig. 225). Mussels are etlible and in Europe thej^ are reared for the market on woven nets, which are submerged at each tide. The pearl mussels (Aviculidse ^) are a group closely allied to the last, but not represented on shores. They are important because they produce the best pearls. Pearl-fishing has been carried on since the earliest preserved historic records. The pearl banlvs of Ceylon are known to have been fished for two thousand years. The finest pearls, however, come from the Persian Gulf. They are gathered there by native divers, who, after tak- ing several deep breaths, either dive down unaided or descend upon weighted ropes. When they can no longer remain under water, they either ascend again unaided or are rapidly drawn up to the boats above. The pearl oysters brought up to the surface are then examined for pearls. The pearl is the secretion of the oyster about a small foreign body, such as a grain of sand or a parasitic worm. This secretion prevents the irritant from injuring the tissues. It is of the â A small bird (avis).. Fig. 227. âOne of the Ledida?, Yoldia, foot protruding below Nat. size. Photo, by W. H. 0. P. 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 Davenport, Charles Benedict, 1866-1944; Davenport, Gertrude Anna Crotty, 1866- joint author. New Yor
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1911
