478 MR W. WEST AND MR G. 8S, WEST ON 
In our previous contribution to Scottish freshwater plankton we recorded a number | 
of algze from Loch Tay, Perthshire, and from Loch Laxadale, Harris; and for the sake ‘ 
of better comparison these records have been included in the tabulated account of the: | 
plankton, along with additions obtained by subsequent collections from these lochs. j 
We have also included in this same table the results of an examination of some — 
material forwarded to us by Mr J. Murray, of the Scottish Lake Survey (Pullar Trust), 
from Lochs nan Cuinne, Ghriama, and Ruar, in Sutherland, and from Loch Morar, in 
Inverness. We obtained permission from Sir Jonn Murray to utilise these results to 
the best advantage, and we have therefore tabulated them alongside the other plankton — 
records. The material from Loch Ruar was both rich and interesting, and consisted — 
principally of Desmids and Diatoms. The Desmids were almost as abundant and con-— 
spicuous as those from Loch Fadaghoda, but were not nearly so diversified in character. — 
The Diatoms, however, were especially noticeable, and constituted fully one-half of the — 
plankton. a 
In preparing this paper we have largely made use of photomicrography. An | 
inspection of photomicrographs, especially those taken under a magnification of 100 — 
diameters, greatly facilitates the comparison of plankton from different lochs, and — 
renders more manifest the distinguishing features of the material. In preparing the 
plankton-material for photography, it is absolutely essential to remove the larger 
animals, such as the Entomostraca, otherwise the thickness of the film of water is 
too great to allow of obtaining a reasonable focus of the majority of the floating objects. 
The photographs used for purposes of illustration are principally of material from Lochs 
Ruar and Fadaghoda, as they indicate very clearly the differences between the Scottish 
plankton and that of most of the lakes of continental Europe. 
Mr Lemmermann, of Bremen, has kindly reported upon the Persdinew and some | 
other flagellate organisms from certain of the lochs. 
II. DetaiteD Account oF PLANKTON OF LOCHS INVESTIGATED. 
Plankton has been examined from the following twenty-four lochs and from the 
River Lochay. The date refers to the date of collection. 
1. Loch Tay, Perthshire, July 1903.—The loch is about 12 miles long and 290 feet 
above sea-level, and is situated in the vicinity of mountains which reach a height of — 
4000 feet. The collections were made from the western part of it during very fine 
weather. Desmids and Diatoms were abundant in the plankton, and there was also 
an abundance of Celospherium Kiitzingianum. 
2. River Lochay, Perthshire, July 1903.—The collections were made from the lower 
reaches of the river before its entrance to Loch Tay. Diatoms were very abundant. 
3. Loch Bawrness, Inverness, Aug. 1903.—This is a small loch situated among very 
rocky surroundings in Moidart. The plankton contained numerous Desmids and a great 
abundance of the Rotifer Anwrea cochlearis, Gosse. 
