226 EIGHTH PACIFIC SCIENCE CONGRESS 



process of pearl formation. K. Isowa tried an experiment on Pinctada 

 martensii and obtained a number of seed pearls by giving chemical 

 or physical stimuli to its aductor muscle and anterior retructor muscle, 

 and patented his method. Y. Matsui, working with Isowa, supposed 

 that a substance similar in function to a hormone was first formed by 

 the stimulus of a wound, and this hormone-like substance in its turn 

 caused abnormal propagation and functional reverses of the epithelial 

 cells in the mantle. On this hypothesis, he made various experiments 

 with fruitful results. As a result of his histological studies of the mantle 

 tissues of Pinctada martensii and Hyriopsis schlegeli, Y. Ojima identi- 

 fied four kinds of secretory cells, but after testing the calcium contents 

 in the tissue, he concluded that these did not make the glands spe- 

 cialized for secreting calcium. Ojima and T. Watanabe are now en- 

 gaged in the study of the structure and the process of formation of the 

 pearl sac. I. Kawakami transplanted the mantle tissue of Pinctada 

 martensii in the gonad tissue, and saw the outer epidermis propagate 

 and complete the formation of pearl sacs in fifteen days, while other 

 tissues degenerated. He also reported his studies on the regeneration 

 of the mantle. 



With regard to the formation of pearls, the important question 

 that the scientists must answer is: What is the mechanism of the cal- 

 cium deposition as well as of the shell formation? Our recent efforts 

 have been directed to discovering a new explanation to answer this 

 question. 



Y. Matsui, S. Tanaka and Y. Uchida are now carrying on experi- 

 ments on the calcium deposition in Pinctada martensii and Hyriopsis 

 schlegeli, using the isotope Cajj. When the animal was kept in water 

 containing Ca^s, the Ca45 absorbed in the internal organs, with the 

 exception of the liver, reached a maximum at the fifteenth hour and no 

 change was observed at the thirtieth hour. In the mantle, the maxi- 

 mum was reached at the sixteenth hour and a reduction was observed 

 at the thirtieth hour. In the shell and the pearl, the presence of Ca^s 

 was noted at the fourth hour. When Ca^s was injected in the body 

 of the mollusc, it was diffused in the internal organs in 1—2 hours and 

 began to be excreted out of the body at the fourth hour. While the 

 shell is mainly composed of calcium carbonate, it also contains a cer- 

 tain amount of conchiolin, which is an organic matter. Many points 

 as to the attributes of the conchiolin are yet unknown. S. Tanaka 

 and H. Hatano have undertaken a biochemical study of the conchiolin, 

 which has led them to discover that the conchiolins in both the shell 

 and the pearl are of the same composition and that proline, oxyproline 

 and sulphur contained amino acid are found in either of the two, 



