252 The Philippine Journal of Science laie 



These artificially produced blisters are cut off from the shell 

 and used as half pearls. Mr. Mikimoto is the first person who 

 tried to apply this method, which has been practiced in China 

 for several hundred years with fresh-water mussels, to the Japa- 

 nese pearl oyster, Margaritifera martensi Dunker. His success 

 was remarkable, resulting in a large culture farm which supplies 

 the world with about 300,000 yens' worth of culture pearls 

 annually. 



His next effort was to improve this culture-pearl method and 

 to produce free, perfectly round pearls. This was rewarded 

 with some degree of success. By a modification of his culture- 

 pearl method, free round pearls are produced; but the method 

 is not reliable, as many operations are required to produce a 

 very small number of free pearls. 



In about 1905 Dr. P. Nishikawa, a graduate of the zoological 

 department of the Tokyo Imperial University and an expert of 

 the Imperial Fisheries Bureau, discovered a new method of pro- 

 ducing free round pearls by pearl-producing mollusks. By this 

 method, which is based upon a totally different principle from 

 that of Mikimoto's, the number of pearls produced is usually 

 from 20 to 50 per cent of the number of operations. He could 

 not see the final result of his own method because of his much 

 lamented death in 1909, although many young pearls were al- 

 ready produced. The experiment was taken up by Fujita after 

 1908, and some necessary improvements were made; while Mr. 

 S. Nishikawa, junior brother of the late Doctor Nishikawa, 

 working upon a practical basis with his brother's method in his 

 private pearl-culture farm, also accomplished some very remark- 

 able improvements. 



The pearls produced by this method, the "Nishikawa method," 

 are free round pearls not distinguishable from natural ones. By 

 several modifications of the method pearls of different structures 

 also can be produced, besides pearls with a structure identical 

 with a natural one in every respect. 



As the result of the experiment with the common Japanese 

 pearl oyster is satisfactory to some degree, the method was 

 extended by Fujita to the so-called black-lip pearl oyster, Mar- 

 gaj'itifera margaritifera Linnaeus, in southern Japan. The re- 

 sult was satisfactory to some degree. 



As the logical sequence of the experiments above described, 

 it is of not a little interest to science and marine industry to 

 test this method with the large gold-lip pearl oyster, Marga- 

 ritifera maxima Jameson. Although the experiments with the 

 Japanese pearl oyster and the black-lip pearl oyster are satis- 



