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An osmotic hatching mechanism is proposed for the Anostracan Branchiopod Chirocephalus diaphanus, PREVOST . In this mechanism, glycerol is thought to accumulate in the egg as a result of the metabolism of the embryo . The osmotic pressure exerted by the egg, largely due to this glycerol accumulation, causes water to enter from the environment . Eventually the hydrostatic pressure thus generated is sufficient to cause rupture of the eggshell . It is recognised that hatching in this Anostracan is a two-staged phenomenon, a process of "breaking", in which glycerol is involved, preceding true "hatching", in which glycerol is not involved . The egg is described and the physiology and ecological significance of the proposed hatching mechanism are discussed .

Seasonal fluctuations of the physicochemical conditions were recorded from five temporary ponds in the New Forest, over a period of two years . Diurnal fluctuations were also recorded . Physicochemical factors studied were pond volume ; air, water and substratum temperature ; water PH ; water conductivity ; and water dissolved oxygen level . The observed patterns of fluctuation are discussed and a concept of pond stability, to which the fluctuations may be related, is advanced .

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