THE FRESH-WATER LOCHS OF SCOTLAND. 
259 
and Loch Linnhe these muscovite-biotite gneisses have been mapped by 
the Geological Survey. These schists and gneisses, which are supposed 
to represent altered sediments, are traversed by numerous veins of 
pegmatite and dykes of diorite, dolerite, and basalt. 
On the watershed between Glen Hurich and Glen Scaddle, on the 
crest of Sgor Dhomhail (2915 feet), there is a mass of foliated granite, 
and, further to the south-west, the later igneous intrusions of the 
Strontian district may enter the Loch Shiel catchment basin. 
Notes on the Biology of the Lochs in the Shiel Distkict. 
By James Murray. 
Of the six lochs surveyed, tow-nettings were taken in four, and a 
shore-netting in a fifth. The biology presented little of special interest. 
Diapto7nus laciniatus was found in two of the lochs (Shiel and Eilt) ; 
these are the most southerly lochs in which this northern species was 
observed by the Lake Survey, though it has been recorded by Dr. Scott 
from one loch (Loch Doon) much farther south. 
Loclh Shiel . — Owing to the great abundance of HolupecUum, which 
choked up the nets, it was difficult to collect other animals in any 
numbers. The most plentiful animals were : Diaptomus gracilis., 
Biaptoiims laciniatus, Cyclops strenuus, Bosmina ohtusirostris , Bytho- 
trephes, Fol yp)hemus, six species of pelagic Hotifers (including Flos- 
cularia pelagicci), and Dinohryon. The plants noted were : Xanthiclium 
antilopeum, Staurastrum gracile, and Staiirastrum hraziliense . Lobelia 
and Littorella were in flower at the upper end of the loch. 
IjocU Dilate . — As compared with Loch Shiel, the most notable 
features of this loch were : the greater abundance of life, the absence of 
Holopedium and Diaptomus laciniatus, and the presence of Diaphano- 
soma hrachyurum in considerable numbers. Among the organisms 
observed were : Diaptomus gracilis, Cyclops strenuus, Syncliceta 
pectinata, Plcesoma truncata, Dinohryon, Beridinium, two species of 
Ceratium (C . hirundinella and C. cornutum), Anaboena flos aquce with 
its adherent Vorticellce. 
Loch Eilt . — Life was abundant, the characteristic animals being 
Holopedium, Diaptomus laciniatus, Cyclops strenuus, Anurcea cochlearis , 
Notholca longispina, and Folyarthra. Leptodora and Bythotrephes were 
scarce. Bosmina ohtusirostris and a variety approaching B. longispina 
were seen. The brilliant red and blue Rotifer, Notops pygmceus, was 
plentiful. Some immature specimens of Diaptomus probably belonged 
to D. gracilis. On the mud in the deepest part of the loch were numbers 
of a pretty little green larva of an insect, enclosed in transparent flask- 
shaped cases. 
