BIOLOGY OF THE SCOTTISH LOCHS 
By JAMES MURRAY, RR.S.E. 
PART I 
THE BIOLOGY IN RELATION TO ENVIRONMENT 
INTRODUCTION 
During the five years of the existence of the I^ake Survey, 562 lochs 
have been surveyed. Biological collections were made in nearly all of 
those lochs, and more than 400 of these collections have been examined. 
Usually only a single collection of plankton was taken in each loch ; 
but in Loch Ness and a few other lochs it was possible to study the 
biology more thoroughly, and to examine the littoral and abyssal 
regions also. From a biological survey made in this manner it is hardly 
possible to make generalisations of any value. Each loch being 
examined only once, and the survey being carried on almost at all 
seasons of the year, the lochs cannot even be fairly compared one with 
another. The amount of difference found between the plankton of 
different parts of the country may in part arise from the fact that 
they were examined at different seasons of the year. This is the more 
probable since it is known that fresh-water plankton is very uniform 
over vast areas. Despite this difficulty, it is, however, certain that 
some very interesting facts in the distribution of plankton organisms 
can be ascertained from an examination of these collections. Their 
chief use, in the meantime, is to enable a census of the inhabitants 
of the Scottish lochs to be made — very imperfect, certainly, but of 
some value to special students, as offering a large body of facts not 
readily got together. 
The biological survey was concerned solely with the Invertebrata 
among animals, and chiefly with the microscopic Algas among plants. 
Of the Vertebrata, the only class which is conspicuous among true 
lacustrine animals, the Fishes, had already been the subject of 
much special study. The same may be said of the aquatic birds ; 
and the other classes of Vertebrata — Mammalia, Reptilia, Batrachia 
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