THE IMPLANTATION OF THE GLOCHIDIUM 

 ON THE FISH 



DAISY YOUNG 

 Assistant in Zoology^. \ 



Three Plates 



The present study, which has been made in connection 

 with the investigations now being carried on at the University 

 of Missouri for the U. S. Bureau of Fisheries on the artificial 

 propagation of fresh-water mussels, was undertaken in order 

 to determine the precise changes that take place in the tissues 

 of the fish as a result of the parasitism of the glochidium. 



The work has been done under the direction of Professors 

 George Lefevre and W. C. Curtis, and I wish to express my 

 thanks for much help and advice that I have received from 

 them. 



THE PARASITISM OF THE GLOCHIDIUM 



As has long been known, the larvae of the Unionida do not 

 complete their development unless they become parasitic on 

 fishes. When they are discharged from the gills of the female 

 mussel they fall to the bottom and remain there with the 

 valves gaping widely open. Unless they succeed in reaching 

 a host they soon die, but when once attachment to the fish 

 has occurred, they quickly become enclosed in a cyst formed 

 from the epidermis of the host, and there pass through the 

 stages necessary for their transformation into young mussels. 

 When the metamorphosis is completed, they free themselves 

 from the cyst and after this time lead an independent existence. 



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