330 Frits Johansen. 



hibernate but how long they take to grow, I do not know; through- 

 out the summer (June — August) I have seen the adults, all of 

 which had about the same size (the size of a pin's head) right 

 from the melting of the lakes. Quite small, red larvae of this 

 mite were found at the end of June 1908 sitting on С/н>о/?о/п «s-pupa 

 and -imago in the water (Hvalrosodden) ^ 



If we take up a little of the green thread-algae, which are so 

 common in the small, sheltered bays by the banks, we find in them 

 a teeming animal life, consisting chiefly of hifusorians, Planarians, 

 etc., and small, brown points drive about in a lively manner; 

 these are the Cladocera, Chijdonis sphaericiis O. F. Müll., which perches 

 on the algae; much commoner, however (especially free-swimming 

 in the water a little further out) is another Cladocera species, namely» 



Daphnia pulex de Geer. 



This characteristic animal occurs in almost dried-up pools and 

 owing to its more pelagic mode of life it is not so much bound to 

 the banks (though this does not apply to the newly hatched young),, 

 but is rather met with in so deep water (up to ca. 1 meter), that 

 there is room for it to swim. Like black grains of pepper dusted 

 out into the water, they are seen "standing" in the water with ex- 

 tended antennae; from time to time they make sudden and powerful 

 beats, then stop and beat again and so on; it is only when they 

 are seeking food among the plants or make from the bottom to the 

 surface or the reverse that they make many beats in succession,, 

 until they reach their goal. Where the water is flowing rapidly we 

 do not find them, probably because, in contrast to Apiis and the 

 Ostracoda, they are more independent ol the water-currents, and 

 thus keep to quieter waters (bays and small pools etc.); here they 

 are often seen in swarms in the still water. If they are swimming 

 about in the water or if the bottom is dark (stony) I have many 

 times experienced, how difficult it is to catch a sight of these trans- 

 parent, dark-brown animals. They are typically littoral forms which 

 live on the microscopic life by the banks of the lake; often we can 

 see them busily feeding on the moss-plants and the like. That they 

 can nevertheless be content with surprisingly little nourishment, I 

 have often proved by keeping them in a glass with water; they 

 were just as lively and numerous 3 days after as on the day they 

 were taken. 



1 As mentioned in the "General Remarks", the same is the case with the 

 earth-mites (Trombidium), as the larvae appear in the middle of June, the adults 

 from May to August inclusive (and probably also the rest of the year). 



