This dialog lists all the lattices that are compatible
with the current settings in the entries 
System,
Lattice and 
Group. When the settings are
impossible, no lattices are shown. When the entries
are empty, all 5 lattices are shown. 
For each possible lattice, GAMGI lists its usual upper-case 
symbol, the description, the systems where it occurs and the 
number of groups with this centering.
Clicking on a listed option in the lattice dialog, has          
exactly the same effect as writing it directly on the 
Lattice entry.