22 PEARLS AND PEARLING 



pearls of this mollusk. The views of these men were 

 confirmed by M. Edgar Thurston in 1894. 



In 1897 M. A. Giard noticed that mollusks produced 

 irregular deposits of conchiolin and lime around the para- 

 site. 



In 1902 Jameson, of London, explained that the for- 

 mation of pearls in the edible mussel, Mytilus cdutis, is 

 due to irritation caused by the Distoma. 



Two noted English naturalists, Herdman and Hornell, 

 after three inspections of the oyster banks, made a state- 

 ment to the effect that they had examined many hun- 

 dreds of oysters and had finally concluded that grains of 

 sand and other inorganic particles did not form the nuclei 

 of pearls, except in unusual instances, such as injury to 

 the mollusk by breaking the shell which would allow 

 sand to enter. According to these English naturalists, 

 the nucleus of the fine pearl of Margaratifera vulgaris is 

 the embryo of a worm of the genus Tetrarhynchus. 



The famous scientist, Dr. L. G. Seurat, in examining 

 the Margaratifera cumingi, or pearl oyster of the Gam- 

 bier Islands found that the formation of pearls is due to 

 irritation caused by the embryo of a worm of the Tylo- 

 cephalum. 



Investigations of American fresh-water mussels for the 

 purpose of learning the origin of pearls have also been 

 carried on by our scientists. 



It has only been in recent years, however, that the sub- 

 ject has engaged their attention. 



The United States Bureau of Fisheries, in charge of 

 Hon. George M. Bowers, Commissioner, has accom- 



