THE FRESH- WATER LOCHS OF SCOTLAND. 
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Synch(Eta pectinata . — Lochs Oich and Uanagan. 
A7iopus testudo . — Lochs Ness and Uanagan. 
Triarthra longiseta . — In five lochs on the east side of the basin; 
apparently a cold-water species. 
GastropuB stylifer. — Loch Ness and five lochs to the east, and Loch 
Aslaich to the west. 
Sarcodina. — Clathrulina was not seen except in the lochs of the 
Great Glen. Nehela hicornis, West, though found in Loch Ness, was not 
got in the plankton, but while dredging in the shallow water of 
Inchnacardoch bay. 
Loch Ness. — Loch Ness was made the subject of a more thorough, 
though still far from exhaustive, biological investigation than any other 
Scottish loch. A very large proportion of all the lacustrine organisms 
known in Scotland have been found in this loch. 
The great majority of the species in all the larger groups — Crustacea, 
Hotifera, Sarcodina — have been got in Loch Ness, the only large group 
not very fully represented being the desmids. Some of the small groups 
have hardly been studied, except in Loch Ness, and it is the only loch 
the abyssal fauna of which is fairly well known. 
To give any detailed account of the hundreds of species found in the 
loch would traverse too much the same ground as the general report 
on the Biology of the Scottish Lochs. There will therefore be given 
here simply an epitome of the biology, and a comparison with the other 
lochs in the Ness basin. 
The Flanktoti. — The plankton is the average plankton of Scottish 
lakes, with a very small admixture of the more local species. It is very 
poor in species, and always very small in quantity. No approach to 
‘‘ flowering ” of the water has been noted. The greatest quantity was 
collected in late autumn, 1903, during the night, when a considerable 
migration from the deeper water to the surface evidently took place, 
as the quantity collected during the preceding day was much less. The 
plankton varies little throughout the year, a fact probably correlated 
with the low annual range of temperature, which is less than 20°*0 
Fahr., while the upper limit of about 60°*0 is rarely touched. 
About half the species of Crustacea remain all the year round, 
those which are absent in winter being Bythotrephes, Polyphemus, 
T^eptodora, and Biaphanosoma. Holopedium was noted by Mr. Scour- 
field, but was never found during the systematic investigation 
afterwards. Diaptomus laticeps, Sars, appears to persist all the year 
round, and was found carrying eggs in March, when the temperature 
is at its lowest. Clathrulina was generally present, and Volvox 
occasionally. 
There is a great contrast between Loch Ness and Loch Lochy in the 
relative abundance of the phytoplankton. Loch Lochy is very rich, 
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