PLATE 3 
EXPLANATION OF FIGURES 
15, 16, 17, and 18 Stages in the formation of the cyst about a hookless 
glochidium (Lampsilis ligamentinus) upon a gill filament of the black bass. Taken 
at 15 min., 30min., 1 hour, and 3 hours, after infection. The transverse lines on the 
filament are the lammellae. 
19 Part of a gill of black bass infected by L. ligamentinus. Showing the 
distribution and orientation of the glochidia in an infection above the optimum for 
this fish. Only the layer of filaments toward the observer is shown. 
20 Glochidium of Anodonta cataracta upon fin margin of carp. 3^ hours 
after infection. Proliferation of the cyst just beginning. 
21 Glochidia, as above, upon fin margin of carp. Showing different stages 
of cyst proliferation, even in neighboring glochidia. 
22 Glochidia, as above, 24 hours after infection. 
23 Hooked and hookless glochidia (A. grandis and L. rectus) embedded and 
developing on a fin margin. The former received in nature and therefore older 
than 28 days, which is the age of the latter. 
