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Part III. — Sixteenth Annioal Report 



XL— THE INA^ERTEBRATE FAUNA OF THE INLAND WATERS 

 OF SCOTLAND.— Part VIIL By Thomas Scott, F.L.S., Mem. 

 Soc. Zool. de France. Including an ACCOUNT OF THE 

 EXAMINATION OF SOME OF THE LOCHS OF SHETLAND. 

 By Thomas Scott, and Robert Duthie, Fishery Officer. 



PRELIMINARY. 



In submitting the results of some further researches into the distribu- 

 tion of the fresh- water invertebrata, I desire first of all to state that, at 

 the request of the Fishery Board, a certain number of the fresh-water 

 lochs of Scotland are at present being examined at stated intervals and 

 apart from the researches hitherto carried on. The purpose of this special 

 work is to ascertain what effect — if any — seasonal variation has on the 

 micro-fauna and micro-flora of the lochs ; whether there is a tendency on 

 the part of these organisms to increase or decrease in number as the 

 seasons vary, and to obtain a more exact knowledge of the effect this 

 seasonal variation has on the development of fresh-water invertebrates 

 and plants. Any other point of interest in connection with this inquiry 

 that may be observed is also being noted. 



The following are the lochs that have been selected for special investi- 

 gation : — ^Forfar Loch, near the town of Forfar ; Loch Leven, Kinross ; 

 Loch Lomond ; Loch Katrine ; Loch Arklet (situated between Loch 

 Lomond and Loch Katrine) ; Loch Achray, Trossachs ; Loch Doon, 

 Ayrshire ; and Duddingston, near Edinburgh. Loch Lomond and Loch 

 Katrine are typical deep-water lochs ; Loch Arklet and Loch Doon are 

 upland lochs, and are situated at a considerable elevation above sea level, 

 Loch Doon being about 660 feet above the sea. Forfar Loch, Loch 

 Leven, and Duddingston, on the other hand, are all more or less typical 

 low-lying shallow lochs. 



These lochs are being examined at intervals of about three months, and 

 the examination is made by tow-netting in the open water from a rowing 

 boat. Two tow-nets of different degrees of fineness are used in this work 

 — one of ordinary fineness for the capture of Entomostraca and similar 

 organisms, and one of silk cloth, very small in the mesh, and made speci- 

 ally for collecting Infusoria, Diatomacea, etc. Suitable portions of the 

 shore are also carefully examined by hand-net, as numbers of invertebrates, 

 instead of voluntarily resorting to the open'water, seek the shelter of the 

 vegetation growing along the shore or in the shallows, and are usually 

 only to be obtained there. 



But in addition to the examination of the lochs referred to, a similar 

 series of observations are being made from time to time on board the 

 Garland into the distribution of the invertebrates and algae of Loch Ness, 

 Loch Oich, and Loch Lochy. The results of this additional work will be 

 incorporated with those of the other lochs, and will no doubt help to 

 throw additional light on the conditions affecting the distribution and 

 development of fresh-water organisms — organisms that directly and indi- 

 rectly are the chief source of food of the fresh-water fishes. 



This inquiry into the seasonal variation of fresh-water organisms is not 

 yet completed, and it may therefore be better to defer giving a detailed 



