PERIODICITY OF THE PHYTOPLANKTON OF SOME BRITISH LAKES. 395 
On the Periodicity of the Phytoplankton of some British Lakes. 
Ву W. West! F.L.S., and G. S. WÉsr, M.A., D.Sc., F.LS. 
(PrATE 19 and 4 Text-figures.) 
| Read 21st March, 1912. ] 
Тхтворостову REMARKS. 
Up to the present little or nothing has been known of the periodicity 
of the British freshwater phytoplankton, a fact which, although rather 
deplorable in view of the extensive periodical plankton-investigations 
carried out in other countries during the past eight or ten years, may be 
attributed very largely to the comparative inaccessibility of the British lakes. 
For the most part, the lakes of the British Islands are situated at con- 
siderable distances from the great centres of population, and for the busy 
individual, with multifarious duties to perform, it is by no means easy to 
visit even a few selected lakes at frequent intervals throughout the year. 
Moreover, the expense incurred is very considerable. 
By the aid of а grant from the Government Grant Committee of the 
loyal Society, and after much trouble, we succeeded in making the 
necessary arrangements for the regular monthly collection of plankton from 
several selected lakes. These were Ennerdale Water, Wastwater, and 
Windermere, in the English Lake District ; and Loch Lomond, Loch 
Katrine, Loch Lubnaig, and Loch Earn, in Scotland. Owing to unforeseen 
difficulties, however, the collections from Loch Harn could only be made for 
four months, and are therefore of small value, and those from Loch Lubnaig 
are likewise incomplete. 
Tn all cases the collections were made from boats by means of the fine 
silken tow-nets we have previously described. 
The first British record of the periodicity of phytoplankton is the account 
given by Fritsch * of the Thames river-plankton, in which he records the 
results of eight collections made from October 1902 to July 1903. Periodic 
collections of plankton were made іп Loch Ness, Inverness, in 1904-05, and ` 
the results were published by Bachmann f in 1907. We have ourselves 
made brief reference to the periodicity of British river- and lake-plankton ў, 
and have also published a complete account of the periodicity of the phyto- 
plankton of Windermere $. These published results are discussed in their 
proper place, along with further investigations, and with the work done by 
investigators in other countries. 
* Е. Е. Fritsch, in Ann. Bot. vol. xvii. (Sept. 1903). 
T Н. Bachmann, in Archiv für Hydrobiol. и. Planktonkunde, vol. iii. (1907). 
f W. & С. S. West, in Proc. Roy. Soc. B, vol. lxxxi. (1909). 
$ W. & G. S. West, in ‘The Naturalist,’ May-July 1909. 
