1. Aodonta grandis and Anodonta imbecillis have been studied with reference to the glochidia and later stages in the life cycles.2. Through experimental infestation, glochidia of Anodonta imbecillis have been reared under laboratory conditions through the period of transformation to the juvenile stage.3. An examination of mature individuals collected at various times of the year yielded only glochidia, showing no evidences of transformation to the juvenile stage.4. The claim that metamorphosis in Anodonta imbecillis occurs in the marsupia of the parent has not been confirmed by this investigation.5. Apomotis cyanellus served as host to the glochidia of Anodonta imbecillis.6. The transformation of glochidia of Anodonta grandis has been followed in experimental infestations using Apomotis cyanellus and Amploplites rupestris as hosts.7. Anodonta grandis may be differentiated from Anodonta grandis gigantea on the basis of glochidial measurements.