BIOLOGY OF THE SCOTTISH LOCHS 
307 
cations, produced by the peculiar environment. They may be rather 
forms or states of the littoral species than varieties or distinct species. 
From the point of view of development the Lake of Geneva is 
very young. The amount of modification produced by the abyssal 
conditions is inconsiderable. If the lake is ancient, measured by 
ordinary standards of time, the modification of species by the peculiar 
environment must be very slow. 
The Danish Lakes. - The Danish lakes, investigated by Dr 
C, Wesenberg-Lund, are all shallow, and a peculiar abyssal fauna is 
hardly to be expected. Dr Lund, in a very instructive paper,^ notes 
six species of marine origin, whether migrants or relicts, in the Danish 
lakes. The three free Crustacea among them, Mysis relicta^ 
Ponteporeia ciffinis^ and Pallasiella quadrispinosa^ are the common 
relict animals in a great many countries. 
Other Lakes. — In the paper above cited Dr Lund gives an 
account of the occurrence of these relict species in Sweden, Norway, 
Russia, Germany, Britain, and North America. 
The Scottish Lakes. — Abyssal Fauna. — Although in the Scottish 
lakes about 20 species of animals are found thoroughly established 
in the abyssal region, none of the peculiarly abyssal forms of the 
Lake of Geneva have been found, except Automolos morgiensis and 
some half-dozen varieties of Rhizopods. Autojjiolos morgiensis is now 
known to be widely diffused over Central Europe. In the Lake of 
Geneva as in Loch Ness it exists in the littoral region as well as in 
the abyssal. Its derivation from the littoral is thus easy, and 
migration from one lake to another is rendered possible, so that it is 
not necessary to postulate an independent development in each lake. 
It would be premature to assert that the peculiar abyssal fauna is 
absent from the Scottish lochs. The observations are very few, 
except in Loch Ness. The collections have not been seen by 
specialists in abyssal faunas, except in the case of the Rhizopods 
worked up by Dr Penard, who did note some few forms which he 
considers peculiar to deep lakes. Possibly if the Mollusca, Crustacea, 
and Worms were seen by naturalists acquainted with the fauna of 
deep lakes, they might detect peculiarities of form among the abyssal 
examples. 
It can only be said definitely that Loch Ness has been examined 
so frequently by different naturalists with various apparatus that it is 
unlikely that any conspicuous peculiar forms have been overlooked. 
If Loch Ness fairly represents the Scottish lochs, there is an exceed- 
ingly meagre abyssal fauna, without a single peculiar species. All 
the species are clearly derivable from littoral species, and indeed the 
1 " Sur I'existence crime Faime Relicte dans le lac de Fiireso," Bull. Acad. Roy. 
des Sci. et des Lettres de Da'nemark, 1902. 
