1904 - 5 .] Study of the Lakes of Scotland and Denmark. 421 
of examining them, they were always covered with coatings* 
often thick, of Diatoms. I found such coatings at the height of 
summer, at a time when they never occur in our country, owing 
to the high temperature of the water; and from what I have 
observed in Danish lakes, I suppose they may possibly also occur 
in the Scottish lakes in winter. I visited Scotland at an 
extremely dry season of the year, when the rivers were only 
moderately supplied with water and the level of the water in the 
lakes singularly low ; on the stony shores and precipitous 
mountain sides I often found a more or less distinct whitish 
band, which on closer examination proved to be due to dried 
Diatoms and other plants, the upper stripe being identical with 
high-water mark. We find a similar band on the stones in our 
lakes in May, but later on the Diatoms are often covered over 
by blue-green Algae.. 
The animal life in the littoral region of the larger Highland 
lochs seemed to me, compared with the Danish lakes, to be 
extremely poor, but it must be kept in mind that I only 
examined the lakes during the season when the animal life of 
the littoral zone is almost everywhere at a minimum ; most of 
those insects which, as larvae, live in the littoral zone, disappear 
in summer as full-grown insects, though they may possibly 
have been numerous at an earlier season. Still, the animal 
life whose home is in the vegetation zone, living or resting 
on the vegetation, is rare compared with our lakes. When 
I had occasion to examine the vegetation, for example in Lock 
Oich, I always found it extremely void of the epiphytic organisms 
so characteristic of most of our submerged fresh-water plants ; still, 
in rapid streams the leaves of Potamogeton natans often constitute 
a support for a great many larvae of Chironomus, Phryganea, and 
of the family Hydroptilidae (I suppose Hydroptila maclachlanif 
as well as for Stylaria proboscidea and Sid a crystallina. Along 
the shores of the lakes I observed very little of the extremely 
rich winged insect life, consisting of swarms of imagos of all 
those insects which as larvae abound in the water, and which 
both in bright sunshine and on calm moonlight nights are 
characteristic of our lakes, and highly attractive to the student. 
Beneath the stones I only found a few Planarians and one or 
