312 THE FRESH- WATER LOCHS OF SCOTLAND 
The admixture of Arctic and southern forms may be accounted 
for by changes of climate, the Arctic species coming south during a 
cold period. The abyssal fauna, clearly derived from the littoral and 
not at all modified, may have originated quite recently. 
These conclusions agree perfectly with those of Professor Forel, 
though in the Lake of Geneva the abyssal fauna has undergone 
some modification. The biology of the lakes indicates a very 
recent origin. 
Phosphorescence. — No trace of luminosity has been observed among 
the fresh- water plankton -fauna, though it has been looked for under 
suitable conditions. The chemical composition of fresh water would 
no doubt lead one not to expect luminosity, yet it seemed worth 
while to look out for it, and put the negative result on record.^ 
CONCLUSION 
The shortcomings of this Report are sufficiently obvious — the 
inequality of the work, and the total neglect of large sections of 
the field. Many points of interest in the biology are not touched 
upon, for lack of time to do so adequately. The including of previous 
work in the same field, especially the work of Dr Scott and Messrs 
W. and G. S. West, which would have greatly added to the value 
of the compilation, was prevented by lack of time to go over the 
literature with sufficient care. 
Finally, the interruption of the work when still far from complete, 
and the consequent necessitv for bringing it to a conclusion somehow, 
caused parts of it to be written with a haste which is highly undesir- 
able when accurate results are aimed at. Nevertheless, with all these 
disadvantages, it seemed well that some summary of the biological 
work done by the Lake Survey should be attempted. If it fail in all 
other respects, it at least provides a trustworthy series of records of 
the life in the Scottish lochs, which should be of some service to other 
students. 
^ It is stated tliat Loch Biiilg in Aberdeenshire occasionally exhibits luminosity, 
but the observations recorded are not conclusive, and both the occurrence and its 
cause call for further investigation (see article by Thomas Jamieson in the 
Aberdeen Free Press, Nov. 19, 1908). 
