1904 - 5 .] Study of the Lakes of Scotland and Denmark. 431 
that “ the majority of the species of Staurastrum and Arthro- 
desmus which occur in the plankton are remarkable for their long 
spines, or long processes with spinate apices. Even those species 
which are normally long-spined increase the length of their spines 
when in the plankton” (1904, p. 554). 
From the results of these thorough explorations I think we may 
conclude, on the one hand, that the home of the plankton Desmids 
is in fact in the pools and moss-covered sides of the hills, from 
which the plankton-flora of the lakes is nowadays recruited, and, 
on the other hand, that some of those forms which, according to 
their primeval structure, were best adapted to plankton-life, are 
now in fact, under the new conditions, about to develop those 
processes (spines, etc.), common to very many exclusively plankton- 
organisms, that we always regard as a floating apparatus. The 
adoption of a pelagic life by the Desmids — a process really going 
on as regards so many species in the Scottish lakes — may be more 
easily understood when we remember that these lakes, unlike most 
other large lakes, offer one of those great life-conditions which so 
many of the Desmids seem to require, viz., peaty water rich in 
humic acid. What I have here set forth is, of course, only a 
theory, but one which may perhaps prove a starting-point for 
further investigations. 
3. The Abyssal Region . — Our knowledge of the abyssal fauna of 
the Highland lakes is at the present time very deficient. Before 
my arrival in Scotland, Mr James Murray had been dredging a 
good deal, especially in Loch Ness. As mentioned in the Intro- 
duction, opportunities were afforded me for dredging in Loch 
Lochy, Loch Oich, and Loch Ness, and from a good steamer I 
used all the various apparatus employed in deep-sea trawling. I 
thus, of course, obtained some idea of the abyssal fauna in the 
lakes mentioned, but still I consider my impressions to be altogether 
insufficient, and the results at which I have arrived need in a 
great measure to be tested and corrected by further explorations. 
The distance from shore at which the alluvial deposits settle on 
the bottom depends in the first instance, of course, upon the 
declivity of the shore. As the shores of Loch Lochy and Loch 
Ness are very precipitous, with depths of 300 to 500 feet only a 
few hundred yards from shore, I suppose that the alluvial deposits 
