BIOLOGY OF THE SCOTTISH LOCHS 
283 
have a resting season, as in some lochs at high elevations only C. 
strenuus is found at the end of winter. The other Crustacea have a 
seasonal limitation. 
All the commonest plankton Rotifers also persist all the year 
round. The season at which a summer species appears in different 
lochs is affected by climate, and by the volume of the lochs. In 
small lochs which quickly warm up in summer they appear early ; 
in larger lochs which remain longer cool they may appear months 
later. No precise limits for the seasonal range of the different 
species can be given, as most lochs were visited only once ; but the 
earliest and latest dates at which they have been observed may be 
indicated. 
Holopedkmi. — Earliest appearance noted, end of April 1903, near 
Inverness ; latest, October 1903, also near Inverness. 
Leptodora. — Earliest, May 1902, in the Ness basin. In Loch 
Ness it was present from July till November 1903 — in October males 
appeared, and in November they predominated. 
Bytliotrephes. — Earliest, Loch Ruthven, end of April 1903 ; latest, 
November 1903, Loch Ness. 
Polyphemus. — Earliest, middle of April, Ness basin ; latest. Loch 
Laoghal, Sutherland, October 1902. In Loch Ness it was found only 
from July to September. 
Diaphanosovia hrachyurum. — Earliest, near Oban, May 1903 ; 
latest, W. Ross, October 1904. 
Latona. — Earliest, Tay basin, May 1903; latest, E. Ross and 
Galloway, August. 
Diaptomus laciniatus. — Earliest, June 1904, Ness basin ; latest, 
October 1902, Sutherland. 
D. wierzejsl'ii. — Earliest, May 1904, North Uist ; latest, October 
1902, Sutherland. 
The seasonal range above indicated cannot be trusted as giving 
the true limits, except for those species {Leptodoi'a^ Bytliotrephes^ 
Polyphemus) which live in liOch Ness. The lochs in which the other 
species live have not been visited earlier or later than the dates given. 
Some of them may endure longer in the season, or even possibly all 
the year round. 
The seasonal variation of the phytoplankton cannot be indicated 
with any precision Loch Ness, which alone has been systematically 
examined during a whole year, has a very meagre phvtoplankton. 
All that can be said about the phytoplankton in this connection is 
derived from single observations of each loch. 
Flowering of the Water. — In the great lakes a marked " flowering'' 
has never been seen at any season. In Loch I^omond there was what 
Dr Bachmann described as a " Wasserbl lithe in August 1905, though 
