REPRODUCTION AND ARTIFICIAL PROPAGATION OF FRESH-WATER MUSSELS. 1 65 



fish and by shipping several hundred to Columbia were able to follow the development 

 of the glochidia under the conditions in our laboratory. The results were probably as 

 favorable as could have been expected under the circumstances. 



In December 1908 a similar infection was attempted with about 6,200 large-mouth 

 black bass and 3,800 crappie in the station of the Bureau at Manchester, Iowa. Upon 

 this occasion the glochidia of Lampsiiis ligamentina were again used in a majority of the 

 infections, similar results being obtained with L. anodontoides, recta, and ventricosa, which 

 were used for the minor infections. The black bass took the glochidia very readily and, 

 having had only a limited experience with this species of fish, we gave them an amount 

 of infection equal to that which had been carried successfully by the rock bass infected 

 at La Crosse in the previous experiments. The infection was estimated at from 2,000 

 to 2,500 glochidia to a fish 4 or 5 inches in length. This proved entirely too heavy for 

 the large-mouth black bass and the mortality among them amounted to about 55 per 

 cent in the 30 days they were under observation. By the third day after the infection 

 the hypertrophy of the gill tissue was so great as to be at once noticeable to the eye, and 

 this was clearly the cause of death. An infection of not more than 1,000 glochidia per 

 fish would have been more nearly the optimum load. 



The crappie did not take the infection well despite longer exposure, the reason for 

 this being the size of their gill slits and their behavior as already discussed, and we do 

 not consider small fish of this species favorable for infection with any of the glochidia 

 from mussels which are of commercial importance. 



Thirty days after these infections the surviving fish were liberated in the Maquoketa 

 River near Manchester, in a situation where the conditions were favorable for mussels 

 and where the presence of a dam below the point of liberation, together with the absence 

 of mussels of this species, made it seem possible that at some later period their appear- 

 ance in this locality might be traced to this experiment. We have never made any sub- 

 sequent examination of this stretch of the river with this in view, a thing which should 

 be done by one of the parties engaged in the field work of the mussel investigation. 



These two experiments in the wholesale infection of fish, while disappointing in 

 some respects, give no indication of any insurmountable difficulties. It is fair to con- 

 clude that a little experimentation under hatchery conditions will make it as easy to 

 carry the glochidia through their metamorphosis in large numbers as we have found it 

 in small lots of fish kept in aquaria. The high mortality of the fish, being so clearly a 

 matter of over-infection, is a thing which can be guarded against without reducing too 

 greatly the load of glochidia which the fish may carry. It is then only a matter of dis- 

 covering the most suitable species of fish and finding out how best to handle them in 

 large numbers. 



One thing which seems necessary for the rapid and uniform infection of fish in large 

 numbers is a device which will bring about a uniform distribution of the glochidia in 

 the water during the whole period of the fishes' exposure. Without something of the 

 sort it will hardly be possible to handle large numbers of fish with constant and uni- 

 form results. We have tried, though not very extensively, two means of effecting 



