THE FRESH- WATER LOCHS OF SCOTLAND. 431 



On both sides of the valley of the Ness there is abundant evidence 

 of intense glaciation of the region. On the elevated plateau west of the 

 Ness valley the direction of the ice-movement varied from 25 to 35 

 north of east. The ice that issued from the Great Glen flowed more or 

 less parallel to the long axis of Loch Ness, that is, in a north-easterly 

 direction, but the trend became more easterly as it approached the basin 

 of the Moray firth. There is a widespread covering of boulder clay, 

 with scattered groups of moraines, along the ridge extending from 

 Dores north-east by Culloden moor. There is also a remarkable develop- 

 ment of fluvio-glacial gravels, high river terraces, and remains of raised 

 beaches at the mouth of Loch Ness, on both sides of the valley of the 

 Ness, and on the south shore of the Beauly firth. 



Loch Ashie is a shallow lake surrounded by drift, with a fine series 

 of moraines on its eastern side. Loch Laide also occupies a hollow in 

 the drift, with small exposures of crystalline schists in places near its 

 margin. Loch Abban lies in a hollow in the stratified deposits at the 

 mouth of Loch Ness, which may be of fluviatile origin. 



NOTES ON THE BIOLOGY OF THE LOCHS OF THE NESS BASIN. 

 By JAMES MURRAY. 



Collections of plankton were made in twenty-seven lochs in this 

 basin. With the exception of the lochs in the Great Glen itself, most 

 of these lochs are at a considerable elevation, occupying the high table- 

 land on the east of Loch Ness, or the higher mountainous tract on the 

 west. 



The situation of the lochs in two alpine masses, separated by the 

 deep cleft of the Great Glen, gives rise to some peculiarities in dis- 

 tribution, most marked in the species of Diaptomus and the more 

 conspicuous plankton Desmids. 



A number of species were only collected on one side of the Great 

 Glen. These peculiarities are probably due to the fact that the lochs 

 to the east of Loch Ness were surveyed in spring or early summer, when 

 the water was still cold, while those to the west were surveyed after 

 midsummer, when they were about at the maximum temperature. 



Difiptomus c/racilis was here, as elsewhere, almost universal, but 

 was not seen in several of the eastern lochs. 



D. laticrp* was in Loch Ness and the other lochs in the Great Glen. 

 It was not seen in any loch to the west, but was frequent in lochs to the 

 east of Loch Ness. In Loch Ness the blue Diaptomus (identified by 



