Аннотация:Partition functions often become tau-functions of integrable hierarchies, if they are considered dependent on infinite sets of parameters called time variables. The Hurwitz partition functions Z = Sigma(R) d(R)(2-k) chi(R)R(t((1))) .... chi(R)(t((k)))exp(Sigma(n) xi(n)C(R)(n))depend on two types of such time variables, t and xi. KP/Toda integrability in t requires that k <= 2 and also that C(R)(n) are selected in a rather special way, in particular the naive cut-and-join operators are not allowed for n > 2. Integrability in. further restricts the choice of CR(n), forbidding, for example, the free cumulants. It also requires that k <= 1. The quasi-classical integrability (the WDVV equations) is naturally present in xi variables, but also requires a careful definition of the generating function.