260 BATHYMETRICAL SURVEY OF 



Loch Dubh. This little loch, remarkable for its great relative depth 

 and temperature conditions, resembling those in a great lake, was 

 examined on two occasions. On the first visit in July, 1902, the surface 

 temperature was 59 Fahr., while on the second visit in March, 1903, 

 the temperature throughout was about 41 Fahr. Notwithstanding 

 this difference in temperature there was little difference in the animals 

 observed on the two occasions. Those found in July were : Diaptomus 

 gracilis (blue and red, grey, red, blue), Cyclops strenuus, Bosmina 

 obtusirostris (small, purple), Daphnia lacustris (all pale red), Eurycercus, 

 Polyphemus, Triarthra, Polyarthra, Anurcea cochlearis, Conochilus, 

 Ceratium hirundinella, Dinobryon. In March all. the same animals 

 were found, except Polyphemus, and there were in addition a few larvae 

 of Corethra (phantom larvae), Notholca foliacea, a second species of 

 Ceratium (C . cornutum less common in lakes), Mallomonas. A very 

 small form of Asterionella occurred. Near the shore large spheres of 

 Ophridium were found on the weeds. In the mud from the bottom were 

 many Rhizopods of the species Cyphoderia ampulla, Difflugia pyri- 

 formis, D. globulosa, and D. arcula. Lobelia and Myriophyllum were 

 growing along the shores. 



Loch na Creige Duibhe. As this loch was only examined by means of 

 a net thrown out from the shore, it is probable that some of the pelagic 

 animals may have been missed. The animals seen were : Diaptomus 

 gracilis (reddish), Cyclops strenuus (yellow), Alonopsis elongata, 

 Chydorus sphcericus, Anurcea cochlearis, Bosmina obtusirostris, Arcella 

 vulgar is. A few of the commonest filamentous Algae and Desmids were 

 seen. Asterionella was scarce. 





