Figs. 40, 41, 42. The Cause of Inverse Symmetry in 

 Snails. In each case the right-hand column represents dextral 

 forms, the left-hand column sinistral ones. 



Fig. 40. Normal and Inverse Symmetry in the Un- 



SEGMENTED EgG AND IN THE FiRST AND SECOND CLEAVAGES. 



