Freshwater Life in North-East Greenland. 333- 



lake and the sun comes to warm up the water, the eggs develop — 

 the more rapidly, the more sunny days there are (thus earlier in 

 the clear summer of 1907, but later in the I'oggy, early summer of 

 1908). As an average for the period of development of the egg, 

 from the time when it is found in the open water until the young 

 appear, I believe that a week is sufficient, as I found the newly 

 hatched young on ^^le 07 (Stormkap). They sat in quantities on 

 the mud-covered moss and herbage near the banks or crawled 

 about here by means of the hooks on their feet; or they come 

 down into the mud, between the line particles of which they are 

 able to bury themselves quickly and neatly. They were never at 

 rest, but moved about constantly here and there, seeking after 

 food, which is plentiful there where they live. When I put them 

 into a glass they sank quickly down to the bottom, though they 

 endeavoured to slacken their downward descent by constantly whir- 

 ling round and round with their legs. Their size was such that 

 they could just be detected with the naked eye, and for this their 

 colour was of assistance as this was conspicuous against the brownish 

 yellow mud. The carapace and the feet projecting from these were 

 pale yellow and inside, the body appeared as a small, reddish 

 yellow spot. On keeping these young ones in a glass with water I 

 observed, how they gradually increased in size ; at the beginning of 

 July (1907) or a little later (under unfavourable conditions, so that 

 the young appeared later (1908)), we meet with the first, full-grown 

 individuals. The conditions are thus quite the same as for Daphnia 

 piilex ; that it is the eggs which hibernate, whilst the 

 adults die in the autumn; in early summer the eggs 

 hatch out the young ones and these then increase in 

 growth in the course о f t h e summer. 



Common to Daphnia and the Ostracods, further, is their wide 

 distribution; not only are they met with in every little pool how- 

 ever small, but they are also common on islands out to sea (Ma- 

 roussia, July 1907), whereas I have never found Apus there. 



Apus glacialis Kr. 



This large and characteristic Entomostracon is extremely common 

 by the banks of all the lakes, mossy hollows etc. in North-East 

 Greenland. It is mostly seen moving over muddy bottom with 

 herbage; it ploughs its way down into the mud with the front part 

 of its head, returns and again repeats the performance, or it buries 

 itself down in the bottom with hasty, wriggling movements of the 



