GENERAL ZOOLOGY 





Digestive gland 



Posterior 

 adductor muscle 



Glochidial 

 hook 



Anterior 

 adductor muscle 



Ganglia 



Foot 



Fig. 13.6. Developmental stae;es of fresh-water mussels. .-1, hooked sjlochidium of Symphynola 

 before attachment to fish. B, young glochidia of Anodonta 24 hours after attachment to the 

 fin of a carp. C, glochidia of Anodonta, 36 hours after attachment, well embedded in the 

 tissue of the fin. /), juvenile mu.ssel, Symphynola, after termination of the parasitic pha.se; 

 note adult structures already formed and persistence of the glochidial hook. (Redrawn from 

 G. Lefevre and W. C. Curtis, 1910, Bulletin of the iiS. Bureau of Fisheries, vol. 30.) 



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