NO. 16.] PROTOZOA ON THE ICE-FLOES OF THE NORTH POLAR SEA. 



melting on the surface, and many great and small fresh-waterponds had been 

 formed on the floes, so much so that it was not even agreeable to walk about 

 without water-tight shoes. We were then in about 81° 39' N. Lat. and 

 122° 9' E. Long. 



fn July I observed that numerous small brownish specks or, as it were, 

 small accumulations of sediment were beginning to form on the ice-bottom of 

 most fresh-water-ponds, especially on the thick floes which had been formed 

 before the previous winter. Similar brownish spots were also formed on the 

 socalled "ice-foot" in the channels along the margin of the floes 1 . By exa- 

 ming these brownish accumulations, from the bottom of the ponds and from 

 the "ice-foot", under the microscope, I found in the midle of July, to my aston- 



Fig. A. Diagram illustrative of the melting of the ice. a, Pond of fresh water on the ice- 

 floe. .6, Layer of fresh melting-water, resting on sea-water (S). c, Ice-foot, d. Lumps of 

 algae floating near boundary between fresh-water and sea-water, e, Small accumulations of 

 algae t on ice-foot, f, Small accumulation of algae in the pond on the ice. 



ishment that they were composed of algae, chiefly diatoms, living and mul- 

 tiplying in this water on the ice; to some smaller extent they were also com- 

 posed of a little mineral dust and of dead fragments of diatoms, Chcetoceras, 

 Coscinodiscus etc., which had evidently been frozen into the ice on its 

 formation; and their shell-fragments had now when the surface layers of the 

 ice ; melted, been set free again and gathered on the bottom of the ponds 

 and on the ice-foot. But among the living diatoms I also observed a good 

 many moving organisms of various kinds. The biggest and most conspicuous 



1 By the melting of the snow and of the upper layers of the floe-ice a good deal of 

 nearly fresh water (with a salinity of 1 or 2 per mille) is formed during the warmest 

 summer months, June, July and the beginning of August. This water either accumu- 

 lates in hollows in the floes to form ponds (Fig. A, a), or runs off into the channels 

 and cracks between the flows where it forms a layer (Fig. A, b), 1 or 2 metres thick 

 (see Memoir No. 9, vol. Ill pp. 305-309) of nearly fresh water resting on the cold sea- 

 water (Fig. A, S). This surface layer of water becomes comparatively warm and has 

 therefore a corrosive>ffect upon the edges of the floes by melting away the ice near 

 the water level, whilst the lower part of the ice situated in the very cold sea-water 

 is not affected, and it consequently projects, often several feet (see Fig. A, c), and is 

 called the ice-foot. 



