184 BULLETIN OF THE BUREAU OP FISHERIES. 



furnishes a demonstration of the feasibility of artificial propagation. Had the food supply 

 in the tank been adequate, it would now be a mussel of about two-thirds the adult size. 



THE ORIGIN AND AGE OF MUSSELS IN ARTIFICIAL PONDS. 



A second line of evidence bearing upon the rate of growth has been obtained in 

 connection with an examination of certain artificial ponds in the vicinity of Columbia, 

 Mo. In this region it is customary for the farmers to construct, for the watering of cattle, 

 ponds in which water is held the year round by the impervious clay soil. We have 

 examined many of these small bodies of water and have records of the approximate, if 

 not the exact, dates of their construction. In 12 of these ponds, the ages of which 

 are from 5 to 40 years, we have found specimens of Lampsilis subrostrata and Unio 

 tetralasmus in some numbers, and in two of the ponds the mussels are present in very 

 great numbers. 



The occurrence of the mussels in the different ponds has been considered, first, 

 with a view to the question of their original introduction into a given pond, and, second, 

 their rate of growth. The first of these two considerations will be discussed here as a 

 matter of convenience, although it should more properly be considered in a section 

 dealing with the introduction of mussels into favorable localities. 



As to their origin in the ponds, we find the facts interesting because it is quite clear 

 that a majority, if not all of the ponds, must have been stocked with mussels which 

 were first introduced as parasites upon fish. The significant facts in this connection 

 are: That we have never found a pond containing mussels but no fish, although there 

 are a number of ponds containing fish in which we have thus far failed to discover any 

 mussels, and that none of the ponds have outlets or other immediate connections with 

 streams in which the mussels occur, but are situated, for the most part, on high ground 

 far from the watercourses, making it impossible that the mussels could have worked 

 their way into these bodies of water by any ordinary process of migration. Since it is 

 very unlikely that persons have introduced adult mussels into so many places by intent 

 or accident, the mussels must have appeared in these ponds by natural means and the 

 most probable of these is their introduction while parasites upon the fish with which 

 the ponds were stocked. The transportation of small individuals attached to the mud 

 on the feet of birds or of terrestrial animals, so often suggested as a means of dispersal 

 in a case like this, is a possible mode of origin, although it seems hardly a probable one 

 in view of the excellent chance the mussels would have of being introduced while still 

 parasites. 



One of the above ponds, which is about 40 by 60 feet in area and 10 feet in depth, 

 is particularly interesting since it contains great numbers of Lampsilis subrostrata and 

 also of the sunfishes {Lepomis humilis and Apomotis cyanellus), which we have found in 

 our laboratory experiments to be very favorable hosts for the glochidia of this mussel. 

 The mussels are of all sizes and the pond has existed for many years. We do not know 

 its exact age nor how long ago fish were introduced. The mussels were first discovered 

 in 1907 and have ever since been found in abundance. Their success is doubtless due, 



