STUDIES MADE IN JAPAN ON PEARL CULTURE 227 



while halogen contained amino acid as gorgonin and spongin, are 

 absent. Y. Matsui, M. Takanami and T. Hirota measured the amounts 

 of amino acids in normal and baroque pearls in a microbiological assay 

 and found that while there was no difference in the amounts of acidic 

 amino acids between the two pearls, there were significant variances 

 in the basic amino acids: namely, in the normal pearl layer, glycine 

 registered 21.9% against 9.8% and leucine 16.4% against 11.3%); and 

 in the abnormal layer of baroque pearls, histidine registered 4.7% 

 against 0.5%, arginine 8.3% against 4.9%, lysine 7.4% against 1.7%, 

 threonine 1.9% against 0%, etc. D. K. Ikenaga, who modified and em- 

 ployed Clark's method, manometrically ascertained that there was a 

 variation in the activities of carbonic anhydrase in Pinctada martensii, 

 corresponding to the specific organs and age of the animal and the 

 seasons of the year. T. Tsuji demonstrated by a histochemical study 

 that while carbonic anhydrase was almost absent in the epithelium on 

 the inside and at the top of the mantle, it was found in abundance in 

 the epithelium contiguous to the shell. He is also carrying on a study 

 on the distribution of nucleic acid. Y. Ojima and Ikenaga, who have 

 undertaken a histochemical study of the alkaline phosphatase in the 

 mantle and the pearl sac of Hyriopsis schlegeli, have discovered that 

 it is distributed in a remarkable amount in the epithelium at the top 

 of the mantle and that while it is found neither in the mucus glands 

 at the side of the mantle adjacent to the shell nor in the epithelial 

 cells of the pearl sac, a considerable amount of it is present in that 

 part of the tissue which has been injured by the insertion of a pearl 

 nucleus. 



Physiological and ecological studies of pearl oysters are also being 

 carried on with great animation, as these can be directly applied to 

 the culture of pearls. Examples are S. Mori's study in the respiratory 

 physiology and daily rhythmic activities of Pinctada martensii, I. Hon- 

 jo's study concerning their reaction to light, N. Kawamoto's study of 

 the artificial spawning in ordinary and diluted sea water, H. Koba- 

 yashi's and J. Matsui's experiments with various degrees of the salinity 

 and temperature of sea water and other environmental conditions, and 

 the studies taken up by S. Kobayashi and the staff of the Mie Prefec- 

 tural Fisheries Experimental Station on the generation and larva of 

 Pinctada martensii. C. Ashikaga, S. Tanaka, H. Hatano and others 

 have made a number of reports on their studies of the chemical com- 

 position and its variation according to the seasons of the year. 



Researches into the water, the bottom of the Pearl Culture ground 

 and the plankton are proceeding under the collaboration of Y. Toyo- 

 hara, J. Yamaji, M. Motojima, M. Morishima, Y. Inoue and others. 



