Let K be a class
of relational systems of a fixed similarity type, n an infinite cardinal. A
system A of cardinality n is (n,K)-weakly universal if each system in K of
cardinality at most n is isomorphically embeddable in A. The object of this note
is to construct 2ℵ0 nonisomorphic finitely generated 0-groups and hence
answer in the negative the following problem attributed to B. H. Neumann. Is
there a group which is (ℵ0,K1)-weakly universal, where K1 is the class of
O-groups?