THE FRESH- WATER LOCHS OF SCOTLAND. 143 



pretty common in the loch. This is a larger species, usually dark blue 

 in colour. It is a northern species, of general occurrence over the 

 north and west of Scotland, but hardly known south of Loch Tay. 

 Daphnia was always very scarce. Desmids of the genera Staurastrum 

 and Arthrodesmus were more numerous than is usual in great lakes. 

 As in Loch Rannoch, skeletons of Clathrulina were abundant. 



Lochs lubhair and Dochart. Both these lochs, being very shallow, 

 had, at the time they were visited, in addition to the usual pelagic 

 species of Diaptomus, Daphnia, and Bosmina, several species in 

 abundance which are not truly pelagic. Chydorus sphcericus, Alonopis 

 elongata, and Alonella nana were as numerous as the pelagic species. 

 Rotifers and Protozoa, especially Rhizopods, were more varied than 

 usual. 



Loch Essan. Life was abundant and varied. Daphnia was of three 

 forms large typical Daphnia lacustris with rounded head, smaller 

 with tall helmet (D. galeata), and an intermediate form. Diaptomus 

 gracilis, some dark brown, some hyaline, Polyphemus, Diaphanosoma 

 brachyurum, Bosmina obtusirostris, and water-mites (Hydrachnidae), 

 which do not usually occur in the open water, were all common. 



Loch Breaclaich. This loch was quite unusual from the great 

 numbers of a Rotifer, Asplanchna priodonta, which formed a 

 " Wasserblut," appearing as a great slimy mass in the net. 

 Diaptomus gracilis (hyaline), Cyclops (dark red), and Diaphanosoma 

 brachyurum were seen. 



Loch na Lairige. The characteristic organisms were Bosmina 

 obtusirostris (large dark brown, and purple) and a species of Conochilus. 

 Daphnia galeata (with tall helmet), Polyarthra, and Diaptomus 

 gracilis (pale, immature) were frequent. A few dark red Diaptomus 

 gracilis, Sida crystallina, and Bythotrephes were also present. 



Loch Lyon. The biology of this loch was notable for its unusual 

 richness. Most abundant were Diaptomus gracilis (pale yellow), 

 Bosmina obtusirostris (with somewhat long spine), Cyclops strenuus (of 

 large size), and Rotifers of many species. Larvae of Diaptomus were 

 exceedingly numerous. 



Lochs Daimh and Giorra. These two lochs are so nearly alike in 

 size and so close together, being connected by a river, that they might 

 be expected to resemble one another in their biology, but they were 

 found to differ greatly. In Loch Daimh, Holopedium was abundant, 

 but very young. Diaptomus gracilis (hyaline, with dark brown eggs) 

 was numerous, and the larvae still more so. Nothing else was found in 

 any numbers. Loch Giorra, on the other hand, had half a dozen 

 common species Diaptomus gracilis (pale yellow), Cyclops strenuus, 

 Daphnia lacustris, Bosmina obtusirostris, Dinobryon, and Tabellaria 

 (two species). Holopedium was not seen. 



