Surprisingly little is known about the influence of salinity on embryo development in crustaceans despite its obvious potential importance to species which breed in inshore estuarine waters. Evidence from the literature is that embryo salinity tolerance may differ from that of later stages in the life history (e.g. Kelley & Burbanck, 1976; Rosenberg & Costlow, 1979; Hartnoll & Paul, 1982; Jones & Simons, 1982; Wear et al., 1986) and such differences may impose restrictions on distribution. Wittmann (1984) referring to mysids, emphasised that an understanding of incubation period and factors influencing it "appears to be a key factor for the understanding of variations in the length and timing of the breeding season, age of maturity, frequency of broods, numbers of young per brood, egg size, and adult body size".