432 Proceedings of Royal Society of Edinburgh. [sess. 
settle on the bottom only at remarkably great depths. It is very 
difficult to dredge upon these almost vertical planes ; and in the 
few instances where a dredgiug gave any result, I never got any 
, finer alluvial deposits, but only stones and gravel, upon which I 
never found any sign of animal life. At the present moment we 
have no knowledge of the animal life on the precipitous sides of 
the lochs from 100 to about 300 feet, but I expect that further 
investigations will show that it is extremely poor. Mr James 
Murray has shown me samples from 300 feet in Loch Hess, con- 
taining many insect larvae, especially Perlidae, Coleoptera, and 
Ephemeridae, as well as many Daphnidae and Rotifera. In the 
dredgings in Loch Ness I never found these animals, and I 
conclude that, especially during the spring, they will be found to 
accumulate in the abyssal region. These forms must certainly be 
regarded as having fallen down the precipitous sides of the 
bordering hills, washed out by the waves, and carried out into 
deep water. Further, I think it quite probable that the rivers, 
especially after heavy rains, may be able to sweep away the 
river-fauna from the rocks and carry it out into the lakes so far 
from shore that it does not subside until depths exceeding 200 or 
300 feet have been reached. Further observations may show 
whether this littoral fauna of the great depths will be starved out, 
or will be able to reach its primary home again. 
I had hoped to find in the lakes of the Caledonian Canal traces 
of the fauna of relict animals, first discovered by Loven in the 
great Swedish lakes, subsequently observed in Finland, Norway, 
Iceland, and North America, and in recent years also in Germany 
and Denmark (1902). I had expected to find both the relicts 
common in all these countries [My sis relicta , Pallasiella quadri- 
spinosa , Pontoporeia affinis), and also those whose home is in very 
deep and very cold water ( Idotliea entomon and Gammarus 
loricatus ), hitherto recorded only from the Swedish lakes and 
Lake Ladoga. It is most extraordinary that the deep fauna of 
the great Swedish lakes has never been investigated since Loven 
drew the attention of the entire scientific world to the existence 
of marine animals in their great depths. I thought that the 
sources of knowledge regarding this peculiar fauna could not have 
been exhausted with Loven’s discoveries, and that modern 
