1904-5.] Study of the Lakes of Scotland and Denmark. 445 
of organic matter, on the whole, very similar to that at the bottom 
of our lakes. The organic life also has some resemblance to that of 
the Da,nish lakes, but still I noticed some very striking differences. 
The band of vegetation visible above water was narrow, but the 
evenly sloping sandy shores, especially along the north-east coast, 
were covered with dense growths of Characea : strangely enough, 
in the deepest parts of the lake, in depths of about 80 feet, I 
found the mud covered with long filaments of blue-green Algae. 
From the explorations of the Lake Survey (1901a, p. 124) we 
know that the mud contains no carbonate of lime. The animal 
life has been studied by Mr T. Scott, to whose paper I refer. 
The molluscan life I found to be much richer than that in 
the Highland lakes, but still by no means so rich as with us. 
Limncea and Planorbis were, both as regards species and in- 
dividuals, relatively few in number ; only in the Characea-growths 
were there great quantities of Valvata , and in the bottom-mud 
Sphcerium , Pisidium, and Anodonta abounded. The Crustacea, 
especially the Cladocera, were represented by numerous species, 
and in the Characea-growths the animal life was extremely rich. 
The quantity of plankton was enormous : I do not remember to 
have seen, even in our lakes, such huge masses of Lejptodora. The 
plankton, at the time I visited the lake, consisted chiefly of this 
Daphnid, with Cyclops strenuus and other Entomostraca. The 
phytoplankton was less conspicuous, Anabcenafos aquce being the 
most predominant, and it might have formed “ wasserbliithe.” 
General Conclusions. 
It will easily be understood that where the alluvial deposits in 
shallow lakes are as copious as in our country, the lakes will in 
the course of time become silted up and overgrown, and will 
finally disappear. When looking at old maps and when studying 
nature we meet with traces of numerous former lakes. Many have 
been drained by man and converted into arable land, but yet in 
such cases man has only forestalled what nature would have 
accomplished in a relatively short period of time. All our lakes 
were formerly much larger, and their form and coast-lines far more 
irregular, the bays having in many cases been silted up, and at the 
