520 MR. W. WEST AND PROF. G. 8. WEST ON 
rich, but, owing to the extensive nature of the districts that 
required investigation, comparatively little time could be devoted 
to the special work of plankton-collection. As the mass of 
material collected is representative of one of the richest and 
most prolific areas in Europe for freshwater alge, it will require 
considerable time to thoroughly work up, and for this reason we 
have thought it advisable to publish the few plankton-alge 
separately. 
The plankton-material was obtained in the usual way by using 
long conical nets of very fine miller’s silk. On some of the lochs 
on which boats could not be obtained, good material was collected 
by taking up a position on rocks at a distance from the shore 
and bailing the clear water through the nets for an hour or more. 
The plankton was found to be very rich in Desmids, and 
several very interesting new species were obtained. 
A few Peridiniex, Rhizopods, Rotifers, &c. have been noted 
from the different collections, and for the determination of 
certain of these forms we express our thanks to Mr. E. Lemmer- 
mann of Bremen. He has also examined some of the material 
from certain of the lochs for alge, and we have included one or 
two species which he noted but which we ourselves had not 
observed. 
II.—DetaitEp Account OF THE PLANKTON OF THE LOCHS 
INVESTIGATED. 
In the tabulated descriptions of the plankton-collections the 
relative frequency of a species is indicated by the letters “cece” 
= very abundant, “ce” = common, “e¢” = fairly common, “r” 
= infrequent, “rr” = rare, and “rrr” = very rare. 
The plankton from the following eleven Lochs was mostly 
collected in the summer and autumn, and is tabulated separately 
from a few small collections made in the South of Scotland during 
the spring. 
Loch Shin, Loch a Gharbh Bhaid Mhoir, Sutherland. 
The collections were made in August 1901, and on both lochs 
boats were used. The material obtained from Loch Shin was 
collected from a broad part towards the south-east end of the 
loch. Although this loch is 17 miles in length, it scarcely 
averages half a mile in width; it is 270 feet above the sea-level 
