Freshwater Life in North-East Greenland. 331 



Among the numerous, dark-brown animals in July and August 

 we find individuals which are transparent and light-brown but оГ 

 the same size; possibly they are some which have just cast their 

 shells. The characteristic, black winter-eggs contain usually 2 eggs 

 in the capsule; seen from the side (surface) they are almost crescent- 

 shaped, whilst from the edge they resemble more a leguminous 

 capsule with 2 seeds. They are exceedingly common in clumps of 

 as many as 10 on blades of herbage and the like or they lie at the 

 bottom of the water by the banks, especially under stones, in holes 

 etc. It is not all the Daphnids, however, which deposit their winter- 

 eggs, as we see partly from the fact, that the dead body of the 

 mother with the egg is often found lying on the bottom, as also 

 partly from this, that from the beginning of September, when the 

 thin ice begins to form, the Daphnids are observed swimming about 

 under the ice bearing their winter-eggs,and they become frozen into 

 the ice when it becomes sufficiently thick; this leads to the death 

 of the mother-animal without hurting in any way the winter-egg. 

 The deposited winter-eggs have a greater specific gravity than the 

 water; if we stir the latter the eggs are shaken up but soon sink 

 again to the bottom, hi the middle of June, however, we ma^^ see 

 a few winter-eggs drifting about at the surface in a vertical position, 

 and as the summer gradually advances we now see more and more 

 of these; under a lens we find that the two eggs in each capsule 

 are now distinctly separated from one another and surrounded by 

 a whitish ring, probably because they are full of air. Placing these 

 winter-eggs in a glass with water and letting them hatch out, I have 

 found that they first lie on the bottom; then as development pro- 

 ceeds they gradually rise up in the water and at last the quite 

 small young Daphnids issue from the eggs — earlier or later accord- 

 ing as the ice by the banks melts quickly or slowly Ч Yet through- 

 out the whole summer (and the whole year for that part) we may 

 meet with unhatched winter-eggs, some of which perhaps never 

 develop or use more than one summer for that purpose. The newly 

 hatched young are a little variable in size (up to ca. 45*1^ of the 

 adults) and have the same form as the older; but they are more 

 transparent and the colour is thus reddish yellow to greenish brown, 

 a great advantage for them, as it is almost impossible to see them 

 in the shallow and quiet water where they live among the herbage. 

 They swim about actively here and find their food among the algae 

 and herbage. In the course of the summer these young increase so 

 much in size that (by keeping them in a glass with water) one 

 can actually observe a daily growth, until in the middle of July 



1 Middle of June 1907, beginning of July 1908. 



