Slu'lls of iiiusst>ls artificially reared and two of the four buttons wliicli have been cut from the shells. 

 — The manufacture of pearl buttons from mussel shells began in 1891 and the rapid increase in the 

 business soon threatened the destruction of the mussels. Tlie United States Government in consequence 

 entered upon a series of investigations as to the practicability of propagating mussels artificially. This 

 is a commercial problem, yet success depends upon a knovi'ledge of the life history of the mussel, which 

 has been gained by various investigators in theoretical work. The life history is unusual : after the 

 young mussel deve'lojis from the egg to a larval form called "glochidium," barely visible to the naked 

 "human eye, it is discharged into the water where it develops further or dies, depending on whether it 

 has an opportunitv to attach itself to some fish. If chance favors it, it takes up the life of a parasite 

 until far enough developed to leave the fish, drop to the bottom of the stream, and enter upon the life of 

 the adult mussel. The task, therefore, of artificially breeding mussels, involves the bringing together of 

 suitable fish and the young, almost microscopic, glochidia. Investigations have shown that a moderate 

 sized fish mav successfuUv carrv from one thousand to two thousand of these parasitic guests 



Cinu-lisii (if il'f l-'nilcd States- Biircfiii of FLsluTirs 

 Part of a group of ponds for experimental work at the United States Fisheries Station. Fairport, 

 Iowa —This is an experiment station for the propagation of mussels as well as for fish culture. It was 

 established bv act of Congress in 1908. The mussels in the illustration above were reared in the pond 

 in the right foreground. Work is carried on at the station to determine what species of f^sh are best 

 suited to act as hosts to the parasitic young of certain species of mussels, and to ascertain the length of 

 the period of parasitism and the life history of the young mussels thereafter, as well as the possibility of 

 rearing them in ponds or in floating crates 



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