REPRODUCTION AND ARTIFICIAL PROPAGATION OF FRESH-WATER MUSSELS. 1 85 



in large part, to the abundance of a fish favorable for their parasitism. Nothing in 

 these specimens, nor in what we know of the history of this pond, gives a clue to the age 

 of the mussels. 



Another pond has great numbers of Lhiio tetralasnins. This pond was constructed 

 in 1901 and during the first year was stocked with fish (the exact species unknowTi). 

 In 1907 it contained a great many mussels as long as 4 inches, and since that year the 

 largest individuals have slightly exceeded this size, which is near the maximum as we 

 know it for this species. It is inconceivable that these unios were introduced as adults, 

 for they are present in great numbers, and the farmer who owned the land was astonished 

 to find them there four or five years after the pond was established, because it was near 

 the entrance to his dooryard and he knew that no one had introduced mussels in any 

 such numbers and that there was no watercourse connecting the pond with any creek 

 in which mussels occurred. These mussels evidently came as parasites upon the fish 

 with which this pond was stocked during the first year and they had reached a length 

 of 4 inches in a period of five years. The abundance of the adults when the pond was 

 six years old and the presence of some smaller specimens made it seem that more than 

 one generation was represented, and hence some maj' have reached this size in a shorter 

 time. The shell of Unio tetralasmus is light and is by no means a good button shell. 

 Still it is not an impossibility, commercially speaking, for we have been assured by one 

 of the leading button manufacturers, Mr. J. K. Krouse, of Davenport, Iowa, to whom 

 we sent shells from which buttons were cut, that a marketable button could be made 

 from them and would be made if there were no other shells available. 



The appearance of Lampsilis subrostrata and Unio tetralasmus and no other species 

 in all the ponds examined suggests the question, why have these two species and no 

 others become established? If they were introduced as glochidia infecting fish, is it 

 likely that the diS'crent lots of fish placed in so many ponds were infected solely with 

 the glochidia of these two species? It seems much more probable that other mussels 

 were introduced in the parasitic stages and that they were not able to sun-ive long 

 upon the bottom of these ponds. We have introduced large adult specimens of Quadrula 

 meianevra and Symphynota complanata into one of the ponds in question and found 

 some of them still alive after two years. This pond had a very soft mud bottom well 

 covered with a layer of black muck filled with the soft coal soot from the smoke of a 

 neighboring power-house chimney and seemed unsuitable for any variety of mussel. 

 It had become, in spite of this, well stocked with Lampsilis subrostrata and is the pond 

 referred to in detail in a previous paragraph. The sursdval here of these specimens of 

 heavy shelled mussels for a period of two years shows that the adults are not at once 

 killed even by unfavorable conditions, and we are therefore inclined to believe that 

 when these species are introduced into the ponds on fish their destruction occurs in the 

 early juvenile stages. 



If a small body of water can be so fully stocked by the scant infection of glochidia 

 obtained by fish in nature, we should be able to introduce mussels hke these into a pond 

 far more effectively by the use of fish which had been artificially infected and to rear 



