. The Cambridge natural history. Zoology. 48 CRUSTACEA BRANCHIOPODA parent is not used as a protection for the winter-eggs, although it is generally, if not invariably, thrown off when the eggs are laid. In the Lynceidae the cuticle is moulted in such a way that the winter-eggs remain within it, at least for a time; the cuticle is occasionally modified before it is thrown off; thus in Camptocercus macrurus the cuticle of the carapace, in the region of the brood - pouch, becomes thickened and darkly coloured, forming a fairly strong case round the eggs. The modification of the cuticle round the

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. The Cambridge natural history. Zoology. 48 CRUSTACEA BRANCHIOPODA parent is not used as a protection for the winter-eggs, although it is generally, if not invariably, thrown off when the eggs are laid. In the Lynceidae the cuticle is moulted in such a way that the winter-eggs remain within it, at least for a time; the cuticle is occasionally modified before it is thrown off; thus in Camptocercus macrurus the cuticle of the carapace, in the region of the brood - pouch, becomes thickened and darkly coloured, forming a fairly strong case round the eggs. The modification of the cuticle round the
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Image ID: RDKY9K
. The Cambridge natural history. Zoology. 48 CRUSTACEA BRANCHIOPODA parent is not used as a protection for the winter-eggs, although it is generally, if not invariably, thrown off when the eggs are laid. In the Lynceidae the cuticle is moulted in such a way that the winter-eggs remain within it, at least for a time; the cuticle is occasionally modified before it is thrown off; thus in Camptocercus macrurus the cuticle of the carapace, in the region of the brood - pouch, becomes thickened and darkly coloured, forming a fairly strong case round the eggs. The modification of the cuticle round the brood-pouch is much more pronounced in the Daphniidae, where it leads to the formation of a saddle-shaped cuticular box, the " ephippium," in which the winter-eggs are enclosed. The ripening of a winter-egg in the ovary of a Dcqjhnia is accompanied by a great thickening of the cuticle of the carapace (cf. Fig. 18), so that a strong case is formed in the position of the brood-pouch. The winter-eggs are laid be- tween the two valves of this case, and shortly afterwards the parent The eggs are. FlQ. 18.—Newly-cast epliippiuni of Daphnia, contaiuing two winter-eggs. moults, retained within the ephippium, from which the rest of the cuticle breaks away (Fig. 18). After separation, the ephippium, which contains a single egg (Ifoina rectirostris) or usually two (Daphnia, etc.), either sinks to the bottom, as in Moina, or floats. The winter - eggs usually go through the early stages of segmentation within a short time after they are laid, but after this a longer or shorter period of quiescence occurs, during which the eggs may be dried or frozen without injury. The sides and floor of a dried-up pond are often crowded with- ephippia, containing winter-eggs which develop quickly when replaced in water; and the resting-stage of winter-eggs pro- duced in aquaria can often be materially shortened by drying the ephippia which contain them, though such desiccation does not appear

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