8o BULLETIN OF THE BUREAU OF FISHERIES. 



of this country and in those of other countries, but more especially in the Mississippi and 

 Great Lakes drainages. For them, however, times changed with the discovery that their 

 shells formed a good material for the manufacture of a universal necessity — buttons. 

 Equal as they were to the vicissitudes of natural conditions, they were unable to with- 

 stand the imchecked ravages of commercial fishery. Thus there has arisen the necessity 

 for measures of conser\'ation — propagation and protection. 



It is the purpose of the present report to present such an account of the structure 

 and habits and relations of fresh-water mussels as will serve to diffuse knowledge of 

 fresh-water mussels and interest in them, as may promote intelligent measures for their 

 conservation and efficiency in propagation and as may stimulate investigation of the many 

 problems presented by thebeha\'ior, distribution, and propagation of mussels. Directed as 

 it is both to the layman and to the scientist, the report must labor under the disadvantage 

 of embodying matter that may seem trite to the scientist and much that may seem 

 overtechnical to the layman. As far as possible, however, the more technical data are 

 omitted or embodied in tables which can be passed over by those who are not interested 

 in the details. 



The first part, on the natural history of mussels or the relation to their environments, 

 embodies data from many sources, but more especially from the general experience of 

 the several authors. In the second part is comprised perhaps the greatest measure of 

 original data gained from experiments and investigations conducted at the U. S. Fish- 

 eries Biological Station, Fairport, Iowa, though there are incorporated also results of 

 the published investigations of Lefevre and Curtis and of others. The third part, pre- 

 senting a summarized account of the structure, does not pretend to offer new data, but 

 rather to afford a background of knowledge of the mussel as a complex living animal 

 with many functions and needs. It might have been placed first but that it seemed best 

 to begin with the subjects which constitute the essential purpose of the paper. 



