ABALONES OF CALIFORNIA EDWARDS, 435 



our knowledge of the origin of pearls from parasitic nuclei. In 

 1902 Jameson traced the life history of a Disfomum from its first 

 host, a duck, to a clam, as its second host, and he succeeded in inocu- 

 lating the edible mussel, Mytilus, by placing it with parasitically 

 infected moUusks, and thus artificially induced the formation of 

 pearls. Herdman, in 1903, found in the pearl oysters of Ceylon that 

 a tapeworm larval cyst may become a pearl nucleus, or that in some 

 cases the secretions may be deposited around sand grains, bits of mud, 

 or a fish or some other small animal, in pockets of the mantle epi- 

 dermis, or again about calco-spherules near the muscle insertions. 

 The surface finally becomes polished, or takes the " orient," and thus 

 reflects the opaline and nacreous tints so highly prized. 



The production of culture pearls dates back to the fourteenth cen- 

 tury in China, and it is probable that the Arabs had a similar in- 

 dustry. The Chinese open the shell of the river mussel, push back 

 the mantle, and introduce metal images of Buddha, which are covered 

 with nacre in the course of six months. Liime drilled a hole through 

 the shell and inserted a pellet of limestone on the end of a silver 

 wire, so that the nucleus might be kept free from the shell during the 

 secretion of nacre. In more recent times the secretion of culture 

 pearls has been induced in pearl oysters by similar methods in vari- 

 ous countries. Bouton, in 1897, at Roscoff, France, bored small holes 

 through the shell of the abalone, and inserted forms made of mother- 

 of-pearl. After some months beautiful pearls were secreted, their 

 size being in proportion to the length of time of the culture. 



In our red abalone a boring mollusk, Pholadidea, penetrates the 

 shell from the outside. It files its way by means of sharp teeth on its 

 shell, and possibly by the secretion of sulphuric acid. The burrow 

 enlarges as the Pholadidea, growing in size, digs its way in. When 

 near the inner pearly layer of the abalone shell the host resists the 

 oncoming Pholadidea by secreting more nacreous matter. Thus the 

 defensive wall, eaten by the Pholadidea, grows inwardly as a mound- 

 shaped projection, the blister pearl. In imitation of this natural 

 process a hole is drilled through the abalone shell and a form is 

 inserted. This form, made of shell, is shaped like a long-shanked 

 collar button, and so placed that the expanded curved base lies 

 against the pearl-secreting mantle. The shank projects from the 

 outer surface of the abalone shell and is there made fast by alumi- 

 num wire, to which a metal tag bearing the serial number is attached. 

 In some cases the wire has corroded, with the loss of the tag. In 

 later experiments the numbers have been filed upon the shell. The 

 black abalone has been used in most cases, although a few experi- 

 ments have been made upon the green abalone. Holes have been 

 drilled through various parts of the shell and different numbers of 

 forms inserted. In addition, spherical forms, without shanks, have 



