XI, D, 4 Seale: Shells of Mindanao and Sulu 253 



factory to a certain degree, there still remains very much to 

 be done before the method can be called very efficient. These 

 necessary experiments can be done only with the gold-lip pearl 

 oyster. 



There are two advantages which invite the application of 

 the method to the gold-lip oyster. They are: 



1. The large size of the gold-lip shell. A full-grown Japanese 

 pearl-oyster shell is about 7 or 8 centimeters in height and length 

 and only 3 or 4 millimeters in thickness. These figures show 

 how small the Japanese pearl-oyster shell is compared with that 

 of the gold-lip pearl oyster and indicate the difference of the 

 nacre-secreting capacity of the corresponding organisms. 



2. The period of nacre-secreting activity. By experiment 

 with the Japanese pearl oyster I have been able to prove that the 

 nacre-secreting function is active from June to November when 

 the temperature of sea water is about 17 °C. In the remaining 

 months it is practically at rest, although there is a very slight 

 degree of nacre secretion. In the warm tropical waters it is 

 probably never at rest while the organism is in healthy condi- 

 tion. My experiment with Margaritifera margaritifera Linnseus 

 in Pelew Island, West Carolines, in February, 1915, has proved 

 that the nacre secretion was active at that time. 



This is the present state of the problem of artificial pearl 

 production in Japan and the reason which urged me to attempt 

 the present scientific trip to the Philippine Islands. 



My plan for the intended experiment here is as follows, pro- 

 vided that the necessary permission is granted by the Govern- 

 ment: 



To get young, live specimens of Margaritifera maxima having 

 a nacre measurement of about 10 centimeters height. This is 

 the most, if not the only, convenient size to work with. After 

 these oysters have been operated upon in a proper way, they 

 will be kept alive in the sea, either scattered over the bottom 

 or suspended in wire baskets some distance above the bottom. 

 From time to time a number of these operated oysters are to 

 be taken out and opened to see the result of the operation. 



On the other hand, it is very important to ascertain whether 

 it is possible to collect very young spats of Margaritifera maxima 

 and to rear them to full-size, adult animals, protecting them 

 from devouring enemies and adverse circumstances by some 

 suitable device, in order to secure the constant supply of the 

 material to work upon in future. 



For the purpose of carrying out the scientific experiment 

 relating to the artificial pearl production by Margaritifera max- 



