THE PEARL OYSTER. 423 



seen by means of a moderately powerful simple lens, merely by holding up a scallop or 

 other shell before the window, so as to al'ow the light to pass through it. 



THE lowest figure in the illustration represents the curious Hammer-shell ; a dark, 

 wnitish species, which, but for the oddity of its form, which somewhat resembles that of 

 the hammer-headed shark, would attract but little attention. As it lies on the ground, it 

 would hardly be taken for a shell by one who was not acquainted with it, the enormously 

 expanded ears and strangely crumpled valves giving it a most unshell-like aspect. This 

 strange form is, however, only to be seen in the adult specimens, or when young ; the 

 shape of the Hammer Oyster is very like that of the pearl Oyster, presently to be 

 described. 



THE floating figure at the right hand of the engraving represents the VARIEGATED 

 SCALLOP, shown as it appears when passing through the water. 



In common with many other molluscs, this creature is able to move with considerable 

 swiftness by means of repeated strokes of its valves, a single stroke carrying it for 

 several yards. 



The animal is very beautiful, its colour being orange or fine scarlet, and the mantle 

 marbled with brown of different hues. A series of round black dots, called ocelli, and 

 thought to answer the purpose of eyes, are ranged around its edge, and surrounded by 

 long tentacular filaments. Like the Oyster and mussel, the Scallop is considered as a 

 delicacy, and eaten dressed in various ways. The shell is of little value, its chief use in 

 these days being as a vessel in which Oysters are "scalloped ;" but in the ancient times 

 it was in great request, as the sign of one who had made a pilgrimage to the shrine of 

 St. James. When at rest, the Scallop lies on the right valve. 



The well-known PEARL OYSTER is one of the most valuable of the shell -bearing' 

 molluscs, furnishing the greater part of the pearls which are set by jewellers and worn 

 by ladies. The specimens represented in the engraving were brought from Ceylon ; but 

 these creatures are also found in other parts of the world, such as Madagascar, Swan River, 

 Panama, &c. Not only the pearls themselves are valuable, but the shells are of great 

 importance in the commercial world, furnishing the best " mother-of-pearl," as the 

 nacreous lining of the valves is called. 



The pearls are secreted by the animal in precisely the same manner as the nacre of the 

 shell, and are, indeed, the same substance, formed into a globular shape, and disposed in 

 concentric layers so as to give that peculiar translucency which is quite indescribable, 

 but is known among jewellers by the name of " water." As to the precise method and 

 object of their formation, opinion differs, the general impression being that they are 

 morbid secretions, often stimulated originally by a grain of sand or some such substance 

 finding admission into the shell. These objects may be obtained by introducing into the 

 shell certain extraneous bodies, around which the nacre is secreted so as to form very 

 good imitations of the pearls formed after the usual manner. Examples of such 

 artificial pearls will be mentioned in the course of the following pages. 



The Pearl Oyster- does not produce its costly harvest under six or seven years of age, 

 and it is, therefore, a matter of importance that the bed should be so managed that the 

 young Oysters may be suffered to remain in peace until they have attained an age which 

 renders them capaoie of repaying the expense of procuring them, and that no part of 

 the bed should be harried where the Oysters are too small to produce pearls. It is hoped 

 that the increasing knowledge of the mollusc and its habits will enable proprietors to sow 

 the sea with pearls just as they sow a field with grain, and that the harvest may be 

 equally certain in either case. 



The Oysters are now obtained by means of men who are trained to the business, and 

 who can remain under water for a considerable time without being drowned. Each diver 

 takes with him a net bag for the purpose of holding the Oysters, puts his foot into a 

 stirrup, to which hangs a stone weighing about thirty pounds, and after taking a long 

 breath is swiftly carried to the bottom. He then flings himself on his face, fills his bag 



