STUDIES IK ANIMAL LIFE. . 127 



ence, that these layers are reversed; in the shell the 

 nacre forms the innermost layer, in the pearl it 

 forms the outermost. Hence the qualities of the 

 pearl depend on the shell, and on the different pro- 

 portions of nacre and carbonate of lime. 



Since we know how pearls are made, may it not 

 be expected that we should learn to make them ? 

 Ever since the days of Linnaeus the hope has been 

 entertained, and it is now becoming every day more 

 likely to be realized. Imperfect pearls have been 

 made in abundance. The Chinese have long prac- 

 ticed the art. They simply remove the large fresh- 

 water mussel from the water, insert a foreign sub- 

 stance under the mantle, and in two or three years 

 (if I remember rightly) they take the mussels up 

 again, and find the pearls formed. In this way 

 they make little mother-of-pearl Josses, which are 

 sold for a penny each ; and I remember seeing a 

 couple of large shells in the Anatomical Museum at 

 Munich, the whole length of which was occupied by 

 rows of little squab Josses, very comical to behold. 

 I was informed that a copper chain of these deities 

 had been inserted under the moUusk's mantle, and 

 this was the result. 



