1904 - 5 .] Study of the Lakes of Scotland and Denmark. 441 
my bottom explorations, where such transformations are figured 
(1901, p. 159, tab. iii.). 
The preceding pages will have shown to what a large extent the 
organic life of a lake may influence the lake itself and its environs. 
We observe the vegetation of the littoral zone being transformed 
into peat, or in other localities being pulverised, and as detritus 
scattered over the lake, reducing the transparency of the water, 
and ultimately find it on the deeper lake-floor^ constituting a part 
of the general precipitation. We see the blue-green Algse of the 
shore corroding the stones, reducing them in size, and the Algse- 
crusts in turn broken off and pulverised by the ice. We are able 
to follow the accumulation, as well as the pulverisation, of shells 
near the shore, and to see the white powder colouring the water 
a greyish- white. We observe whole layers of lime (often several 
feet thick) arising from the precipitated stems and leaves of 
Characea, and are also able to show that the percentage of lime 
on the bottom is raised by the lime dropping down from the great 
leaves of Potamogeton. We see the huge plankton masses deter- 
mining the colour of the water, affecting the quality of the air 
contained in the water, causing accumulations of gases unfit for 
the respiration of animals, and greatly reducing the transparency 
of the water. We are able to recognise the once-living plankton 
as skeletons in the deeper layers of water, and to show how the 
nature of the lake-bottom is mainly determined by the character 
of the plankton, and, furthermore, that whole layers are derived 
from the accumulation of Diatom skeletons. We also note how 
the different precipitations are eaten by the bottom-fauna and 
converted into excrementa, and that the excremental processes 
result in layers having a lesser amount of organic matter and a 
greater amount of inorganic matter than if the precipitations had 
not been subjected to the digestive action of the bottom-fauna. 
B. The Scottish Lakes. 
As the result of my investigations on the Danish lakes, I have 
dwelt at some length upon the manner in which the fauna and 
flora influence and react upon the general character of the lakes 
themselves, thereby transforming the conditions of life common 
to all organisms in the lakes and their surroundings. From the 
