a1 Department of Mathematics Tokyo University of Education Otsuka, Bunkyo-Ku, Tokyo.
Various investigations on (E, M)-categories are given by many authors. Recently, Herrlich (to appear) and Strecker (1972) gave interesting results on relations between factorizations (E, M) on nice categories and epireflective subcategories of . Factorization (E, M) treated by them satisfy that E Epi. In this paper we shall consider factorization structures (E, M) such that E⊃Epi in the category of all topological spaces and study relations between these structures and some subcategories of . Our results are quite different from those in Herrlich (to appear) and Strecker (1972) and are rather related with the results in Herrlich (1969). Herrlich (1969) defined limit operators on and gave a one-to-one correspondence between suitable limit operators and bicoreflective subcategories of . We shall consider two kinds of factorization structures on and show that the first ones correspond to bicoreflective subcategories which are closed under closed embeddings, the second ones correspond to bireflective subcategories which satisfy that the classes of all reflections are closed under closed embeddings (see Proposition 11) and these correspondences are one-to-one.
(Received July 02 1974)