940 TRANSACTIONS OF THE [MAY 138, 
a, b a b 
y © 
Fic. 3. Reduction variation; Origin Fic. 4. Reduction variation; Origin 
retained; Insertion reduced. retained; Insertion reduced. 
a a 
x y 
Fic. 5. Reduction variation; Origin Fic. 6. Reduction variation; Origin 
and Insertion reduced; Points re- and Insertion reduced; Points ex- 
tained. changed. 
a b 
Yo x 
Fic. 7. Reduction variation; Origin Fie. 8. Reduction variation; Origin 
and Insertion reduced; Points re- and Insertion reduced; Points ex- 
tained. changed. 
