VII 1 



OF HEXAGONAL SYMMETRY 



501 



Fig. 180. An "artificial tissue," formed by coloured drops of sodium chloride 

 solution diffusing in a less dense .solution of the same salt. After Leduc. 



Fig. 181. An artificial cellular tissue, formed by the diffusion in gelatine of 

 drops of a solution of potassium ferrocyanide. After Leduc. 



