ABSTRACT
Given z in Z let Lz be the union of all σ-null cells I in K which contain 2. Lz is a nondegenerate interval by the definition of Z. If J is any σ-null cell which meets Lz it must meet some σ-null cell I containing 2. So I U J is a σ-null cell containing 2, hence must be contained in Lz. This implies that Lz is a component of Z. Since the components of Z are disjoint and nondegenerate there are only countably many of them. Thus we need only prove that for each z in Z
(1) L z is a countable union of σ-null cells.
