The Cellular Basis 



193 



Figs. 70, 71, 72. The Cause of Inverse Symmetry in Snails. In each 

 case the right-hand column represents dextral forms, the left-hand column 

 sinistral ones. 



Fig. 70. Normal and Inverse Symmetry in the Unsegmented Egg 

 and in the First and Second Cleavages. 



