1904-5.] Study of the Lakes of Scotland and Denmark. 413 
As the depth of the lakes increases very regularly from the 
shore outward, and as the different plants are on the whole limited 
to certain depths, the vegetation arranges itself in zones (see fig. 2). 
For details I may refer to the excellent work of Professor Warming 
(1895),* and will here restrict myself to the following remarks. 
In most of our larger lakes we have a narrower or wider shore- 
zone, mainly characterised by Seirpus lacustris and Pliragmites 
communis . Further out we shall find zones of Potamogeton lucens 
and perfoliatus and some other plants, especially Batrachium , 
Myriophyllwn, and Ceratophyllum. Still further out, by dredging 
on the bottom, we find a zone formed of Characea and some Fonti- 
nalis , which extend to a depth of 8 or 9 metres (25 or 30 feet), 
and beyond this limit we usually find no higher plants. With 
the exception perhaps of the outer border of the Characea zone, 
all these zones of vegetation die off in winter, leaving only their 
resting organs, their rhizomes, etc., on the bottom. The higher 
plants are in summer nearly always covered by a very rich 
epiphytic vegetation of blue- green Algae, Diatoms, and green 
Algae. On the windward side of the lakes the vegetation is, of 
course, less abundant, and here we often find beaches of stones 
and gravel, without any higher plants. The stones themselves in 
all our lakes are in winter covered with a rich brown coating of 
Diatoms, which in summer often disappears, but in several lakes 
its place is taken by a crust of greyish lime deposited from the 
blue-green Algae, as in many of the Swiss lakes. 
The plentiful vegetation is the home of an abundant and re- 
markable animal life : of the higher invertebrate groups we 
^ specially notice many larvae of insects, — -of Diptera, Phryganidae, 
Ephemeridae, Libellulidae, certain Coleoptera, and a few Neuroptera 
(Sialis) ; of the Crustacea there are Amphipoda (Gammarus pulex, 
Pallasiella quadrispinosa), Asellus, Daphnids and Copepods in 
great abundance ; besides many Rhabdocoela, a few Dendrocoela 
and Oligochseta, very many Rotifera, a very rich Protozoan fauna, 
and a great many snails and mussels. Beneath the stones we also 
find numerous organisms, especially Phryganidae, Ephemeridae, and 
Planaria, and on the upper sides of the stones snails are nearly 
everywhere found. 
* This work will shortly appear in English, translated by Professor Balfour. 
