BIOLOGY OF THE SCOTTISH LOCHS 
289 
Bosmijia longispina was found in Loch Morar all the year round. 
In Loch Ness, Daphnia having rounded head, and Daplinia more or 
less galeate, were found all the year round. These lochs are among 
the largest lochs, and the annual range of temperature is very low. 
It mav be that smaller lochs would give more definite results.^ 
The Littoral Region 
The littoral region is the most populous part of a lake. The 
existence of a rooted chlorophyllaceous vegetation is only possible 
there, and this in turn supports a rich littoral fauna which otherwise 
could not exist. The moderate temperature of the open M^ater of 
lakes is unfavourable to the growth of many forms of life, but the 
weedy margins, becoming heated in warm weather, favour the growth 
of many forms which are most at home in ponds. As there are no 
peculiar abyssal species, and as most of the true plankton species may 
be taken even among the weeds, the littoral region, well studied, gives 
an epitome of all the life of the lake. 
The species inhabiting the littoral region need not, then, be 
detailed. The whole " Census of Species forming the second part of 
this paper may be taken as equivalent to the littoral fauna and flora. 
As, however, the number of plankton species is small, and that of 
abyssal species still smaller, it follows that the majority of the species 
are confined to the littoral. 
Insect larvae of many kinds are found under stones or among 
weeds, only Chironomus being commonly found in the plankton or 
the mud. The great majority of the Cladocera, and the Copepods 
of the genus Cyclops and the family Harpacticidge, are only found 
in this region. The Water-Mites only occasionally stray into the 
plankton. Nearly all the Rotifers, all the Gastrotricha and Tardigrada, 
exist only in this region. The Mollusca, except for the one Pisidmm 
and a stray Limncea, are only found here. The Rhizopods are all 
found in the littoral region, but nearly all are supposed to extend 
into the abyssal. The Chlorophycea? are in favourable localities 
more abundant in the plankton, yet the majority of the species 
are littoral. 
The littoral region has a mixed population. All lacustrine 
animals and plants are aquatic in the sense that they can only perform 
all their functions when surrounded by (at least a film of) water. 
Yet is it true that perfectly aquatic species form only one section 
of the community, and that another large section consists of animals 
and plants called terrestrial. One group of such species is the 
so-called semi-aquatic plants, some of which can live permanently 
1 See paper by J. Hewitt, p. 335. 
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