1433 
question thus belongs as a special case to the group 7, = {JI,, 7", 
where I, is: 
Mel WB as IT{~ MSa MuSa MBEa M' WE 
§ 7. Final remarks. In the same way we can also study the 
cubic model with 48, 24 and 8 electrons respectively, and also the 
models with other numbers of electrons. We may still draw the 
attention to the problem of the s-t-symmetrical relation between the 
different shells of an atom with respect to the above said on the 
periodicity of the configurations of the electrons. 
Finally the following may be remarked: 
When a certain number of electrons is moving in such a way 
that s-t-symmetry exists, it is evident from the preceding that 
perhaps no pure space symmetry element exists. In the equations 
of motion given by LANDÉ for one of four electrons the remaining 
space symmetry of the four electrons was taken into consideration. 
These equations proved to possess the symmetry of the group 7 of 
SCHOENFLIES, so that the four-bodies-problem of the four electrons 
was reduced to a one-body-problem. From the preceding we now 
see, that this reduction could only be the consequence of the existence 
of the s-t-symmetry of the electron configuration in the equations; 
and that this symmetry would not suffice when the time-symmetry 
parts are omitted. It may be verified easily though that, in the cases 
discussed above no change is brought into the conclusion by this 
remark. We have seen moreover, that the appearance of s.-t.-sym- 
metry instead of space-symmetry was always connected with the 
coincidence of two or more orbits; and algebraically this is expressed 
by boundary conditions, not by a property of the equations of 
motion.. 
