xviii Transactions of the Royal Society of South Africa. 
Vorlaender's experiments on such layers in convergent light show the 
well-known rings and crosses of uniaxial crystals. He believes that the 
pseudo-isotropic layers have space-lattices. When Eoentgen rays are 
passed through such layers no interference phenomenon is obtained ; hence 
there is no space-lattice. This indicates that — 
1. The molecule itself is a small crystal possessing magnetic axes. 
2. A change in the structure of the molecule itself causes a change in 
the form of the crystals of the same substance. 
