no BULLETIN OF THE BUREAU OF FISHERIES. 



physical conditions of the waters in which different species thrive and attain their 

 maximum growth, food supply, enemies and diseases, rate of growth and the influence 

 of environmental factors upon it, and the behaxnor of glochidia and fishes as parasites 

 and hosts, respectively. 



The results that have already been obtained, although far from complete, will 

 ser\'e as a basis for future investigations, while the lines of attack in the main prob- 

 lems have been definitely indicated. We have proceeded far enough to make it clear 

 that the ultimate end of the investigation is assured, and with adequate facilities for 

 the infection and care of large numbers of fishes and for the maintenance of the young 

 mussels during the early stages of growth followng the metamorphosis, the final success 

 of the work can no longer be in doubt. The essential facts in the life history of the 

 Unionidae are known; the breeding seasons and habits of the commercial species have 

 been sufficiently determined; the general conditions of infection and of the parasitism 

 of the lan'a have been learned experimentally; and the entire feasibility of artificially 

 propagating at least certain species of fresh-water mussels has been clearly demonstrated; 

 while the requisite conditions for placing artificial propagation on a practical basis are 

 now thoroughly understood. 



The writers' personal attention has in the main been directed to a study of the 

 conditions of reproduction in the group and the parasitism of the larva in their bearing 

 upon the problem of artificial infection of fishes with glochidia, while such phases of 

 the investigation as geographical distribution, systematic studies, and a number of 

 special ecological problems have been in the hands of other investigators. 



At the recently estabUshed biological station of the Bureau of Fisheries at Fairport, 

 Iowa, while construction was still in progress, the work of propagating some of the 

 commercial species was inaugurated, and the excellent facilities of the station, which 

 has been especially designed for the purpose, are now being utilized by members of the 

 staff in attacking fundamental problems of both a scientific and an economic nature. 



For the past five summers a number of field parties have been equipped and sent 

 out each year by the Bureau to collect fresh-water mussels and to obtain the fullest 



Note. — It is a pleasure to state that a generous grant of money made by the National Association of Pearl Button 

 Manufacturers in the interest of the investigations enabled us to purchase a collection of books and pamphlets, dealing with the 

 literature on the Unionids. which has been of invaluable assistance in the course of the work. To individual members of this 

 association, especially to Mr. J. E. Krouse. of Davenport. Iowa, Messrs. W. F. Bishop and Henry Umlandt, of Muscatine, Iowa, 

 and Mr. D. W. MacWillie, of La Crosse. Wis., we are indebted for many courtesies aud for shipments of live mussels which they 

 have repeatedly secured for us. Many others have at times assisted us by sending us material, and in this connection we take 

 especial pleasure in thanking Prof. U. O. Cox, of the State Normal School at Terre Haute, Ind., who has kindly furnished us 

 on several occasions with valuable lots of gravid mussels from the Wabash River. 



To a number of our students, who in various capacities have been of service to the investigations, we owe much, and among 

 them should be mentioned Miss Daisy Young, Messrs. Howard Welch, F. P. Johnson, W. E. Dandy, L. E. Thatcher, 

 and especially Mr. W. E. Muns. who acted as our assistant in this work for over two years. 



Lastly, it is a pleasure to acknowledge our obligation to Mr. G. T. Kline, the biological artist of the University of Missouri, 

 who has contributed much to the value of our work by the beautiful and accurate drawings with which he has illustrated this 

 and previous papers published by us. 



By permission of the Commissioner of Fisheries, we have had the privilege of publishing, in advance of this more detailed 

 report, the following papers of a preliminary nature: E.^periments in the artificial propagation of fresh-water mussels 

 (Proceedings of the Fourth International Fisher^' Congress, Bulletin of the Bureau of Fisheries, vol. xxviii. 190S); Themarsupium 

 of the Unionidre (Biological Bulletin, vol. xix. no. i, 1910); Reproduction and parasitism in the Unionidse (Journal of Experi- 

 mental Zoolog>', vol. IX, no. I, lyio); Metamorphosis without parasitism in the Unionidae (Science, vol. xxxm, no. S57, 1911). 



