332 BATHYMETRICAL SURVEY OF 



elegans, Micr aster ias furcata, Staurastrum furcigerum, Xanthidium 

 subhastiferum. 



Loch an Dithreibh. Bosmina obtusirostris, var. longispina, Flos- 

 cularia pelagica, Staurastrum ophiura, cysts of Ceratium. Animal 

 life (both as to individuals and species) was very scarce, while the 

 smaller algae were conspicuous. 



Loch na Meide. Diaptomus laticeps, D. laciniatus, Cyclops gigas, 

 Daphnia (galeate), Ilyocryptus acutifrons, Gastropus stylifer ( = Notops 

 pygmceus), Staurastrum ophiura, S. arctiscon, 8. pseudopelagicum, 

 Micr aster ias apiculata, var. fimbriata. This loch was remarkable for 

 the abundance of both animal and plant life ; about eighty species of 

 organisms were found in the first cursory examination. The true 

 plankton was not, however, particularly rich, there being a very large 

 admixture of littoral species. Ilyocryptus acutifrons was first observed 

 in Scotland in this loch, though it was afterwards found that it had been 

 collected in Loch Shin at an earlier date. 



Loch Naver. Diaptomus laticeps, Bosmina obtusirostris (small, with 

 long spine), Floscularia pelagica, Gastropus stylifer, Staurastrum 

 ophiura, S. arctiscon, S. grande, Micrasterias conferta, M. furcata 

 (typical, also a variety having the whole surface covered with hemis- 

 pherical papillae of unequal sizes). 



Loch Chaluim. Daphnia (two forms, first with small rounded head, 

 second with very large broad, depressed head, many males), Syncluzta 

 pectinata, Gastropus stylifer, Polychcetus collinsi, Staurastrum ophiura, 

 S. arctiscon, S. furcigerum. 



Loch Laoghal. Bosmina obtusirostris, var. longispina, Floscularia 

 pelagica, Triarthra longiseta, Clathrulina elegans, Staurastrum pseudo- 

 pelagicum, S. jaculiferum. 



Loch Creagach is connected with Loch Laoghal by a wide channel, 

 and stands at the same level. The biology calls for no separate mention. 



NOTE ON Clathrulina elegans, Cienk. Skeletons of this animal were 

 abundant in the deep lochs Hope and Laoghal. In an earlier paper* 

 an attempt was made to account for the presence of these empty shells 

 in so many of the Scottish lochs, and as a general rule only in large 

 ones, on the supposition that they were derived from the shallow waters 

 in which C '. elegans is known to live, attached to water-plants by a 

 slender stalk. Up till quite recently only empty cases had been found, 

 or at most an occasional shell containing an encysted mass of protoplasm, 

 and on these facts was based the suggestion put forward as to their 

 origin. A fresh aspect is put upon the inquiry by the recent observation 

 that in Loch Lochy, where the animal was abundant in August, 1905, 

 when the loch was visited in company of Prof. Bachmann, most of the 

 shells contained living animals, which extended their pseudopodia and 



* See p. 291. 



