Howard. — The Catfish as a Host 67 



Obviously a more direct solution of the problem would be 

 secured by a study of natural infections, i. e.. fish taken at 

 large are examined for glochidia and when present these are 

 determined as to species, condition, etc. 



In an investigation of some members of the Quadrula 

 group of mussels which I have carried on this spring and 

 summer the above method was employed. I made examina- 

 tions of as many species of local fish as were obtainable, 

 identifying as far as possible such glochidia as were found. 

 Some glochidia, because of peculiarities of form or size, 

 were readily determined, while others were less easily iden- 

 tified because of less apparent differences. In this study I 

 found of great assistance the excellent preparations and 

 drawings of glochidia by Messrs. T. Surber and H. W. 

 Clark, of this station, who kindly placed their material at 

 my disposal. 



This line of investigation, as well as answering the main 

 question for which it was undertaken, revealed some other 

 interesting points. Among these may be mentioned the 

 predilection of several species of mussel for one kind of 

 fish ; for example, "the Sheepshead," Aplodinotus grnn- 

 niens, was found to carry commonly the glochidia of Lamp- 

 silis Icevissima, L. gracilis, L. alata, Plagiola donaciformis 

 and others. This fish feeds upon mussels and so we have 

 an explanation of the presence of these thin shelled species 

 upon its gills. 



Another observation for these species, so far as I know 

 previously reported for L. Icevissima only was the extensive 

 growth beyond the glochidial shell while still on the gills of 

 the host. 



Some cases of remarkably full infection have been found, 

 but a small number seems more common for natural 

 infection. 



The absence of glochidia uniformly in certain species of 

 fish is quite striking, as in the German carp, Cyprinus carpio, 

 Linnaeus, mentioned above, as well as the garpike. Lepis- 



