434 BATHYMETRICAL SURVEY OF 



and Loch Ness very poor. The two lochs are only some 10 miles apart, 

 and are apparently under almost identical conditions. Loch Lochy, 

 being in an almost uninhabited district, should be purer than Loch 

 Ness, but a slight pollution is generally favourable to vegetable 

 growth. 



Littoral region. Though there are only a few sheltered bays in 

 Loch Ness where littoral vegetation can establish itself, the micro- 

 fauna and microflora found among the larger vegetation are very 

 considerable, and constitute, indeed, the chief part of the species in 

 the loch. 



A great many of the animals extend downwards to a very consider- 

 able depth, and about 40 species (exclusive of Rhizopods), including 

 many Crustacea, Rotifers, Tardigrada, Worms, and the larvae of many 

 insects, have been collected as far down as 300 feet. Shells of all the 

 Rhizopods extend to the greater depth, and many live at greater depths 

 than 300 feet. 



In Inchnacardoch bay Mr. Scourfield found Ophryoxus gracilis for 

 the first time in Britain; and the rare Ilyocryptus agilis, previously 

 known in several places in England, was got in the same locality. 



Abyssal region. In Loch Ness a large proportion of the littoral 

 species extend to about 300 feet in depth, probably because of the very 

 steeply sloping sides. Those species only are considered as truly abyssal 

 which are generally distributed over the mud, into the deepest part of 

 the loch. A small association of animals is found thus distributed, 

 and the abyssal region, being defined as the bottom where this associa- 

 tion is found almost free of admixture, must be considered to begin 

 at about 300 feet. Exclusive of Rhizopods, there are about a dozen 

 animals constantly found in this region, comprising 1 Mollusc, 

 Pisidium pusillum, Gmel. ; 3 Crustacea, Cyclops vir id-is, Jurine, 

 Candona Candida, Mull., and Cypria opthalmica, Jurine; 3 worms, 

 Stylodrilus gabretece, Vejd., Automolos morgiensis (Du Plessis), and an 

 undetermined Oligochsete; 1 insect, Chironomus (larva); several 

 Infusoria, parasites on the Molluscs and Crustacea. 



Several other species occur casually at great depths, such as Hydra, 

 Limncea, Lynceus affinis, and Proales daphnicola. 



A small char, Salmo altinus, was dredged at a depth of over 500 

 feet. 



Larvae of Tanypus and some other diptera are frequent, but less 

 constant than Chironomus. 



Rhizopods. Dr. Penard has identified about 40 species and varieties 

 from depths of more than 300 feet. They thus constitute the greater 

 part of the species in our abyssal region, but their presence there 

 is of little special interest, and there are only some half a dozen 

 species and varieties which are doubtfully supposed to be peculiar to 

 deep lakes. 



