48 CRUSTACEA—BRANCHIOPODA CHAP. 
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-eges are enclosed. The ripening of a winter-egg in the 
ovary of a Daphnia 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 
Fra. 18.—Newly-cast ephippium of Daphnia, 
containing two winter-eggs. moults. The eggs are 
retained within’ the 
ephippium, from which the rest of the cuticle breaks away (Fig. 
18). After separation, the ephippium, which contains a single 
eve (Moina 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 to be necessary for development. Under 
normal conditions large numbers of winter -eggs remain 
quiescent through the winter and hatch in the following 
spring. 
The individual developed from a sexually fertilised winter- 
