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 microfiora 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 viridis, Jurine, 
Candona Candida, Miill., and Cypria optlialmica, 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. 
