EXPLANATION OF PLATES 



All figures are drawn with the Zeiss camera under Zeiss ^-j oil-immersion 

 objective and Zeiss compensating ocular 18, at the distance of 250 mm. tube 

 length 160 mm. By reproduction they were reduced to three-fourths of the origi- 

 nal. Figures 2, 3, 5, 7, 10, 14, 15, 30-33, 37-39, 46, 47, 49, 50, 55, 57, 69, 67, 73, 

 79-83, 86, 90, 92, 95 are from preparations stained by iron-haematoxylin, after 

 fixation with sublimate; the others from Meves preparations. 



PLATE 1 



EXPLANATION OF FIGURES 



ri to ^ Ciliated cells from the foot of Anodonta, figure 3 surface view. 

 -4, 5 From gills of Andonta, figure 4 lateral cell, figure 5 surface view of the 

 lateral surface of the gill-torus, a, lateral cell; b, corner-cell. 



6 to 8, 16 to 20 From the intestine of Anodonta, figure 16 surface view. 



9, 13 to 15 From the intestine of Helix. 



10 to 12 From the hepatic duct of Helix. 



272 



