72 Transactions of the Royal Canadian Institute 



(25) 



and 



02 - _ _ 



7=^ = ^+cx—az, 



"3 — 1 — T 



i=^ = y+ay-hx. 



Vap 



From these and equations (23) we deduce 



_ _ 1 1 



SacL -\- Sa a = + = , 



by Enneper's theorem. This is the relation that must be satisfied by the 

 functions a, b,c, a, ^,y, a,b,c,a,^,y "i order to comply with the 

 conditions of the problem. Geometrically, it expresses that the two 

 families of complexes are in involution. 



McGiLL University. 



