THE FRESH-WATER LOCHS OF SCOTLAND. 
33 
most abundant. Cyclops, especially G. strenuus, was also plentiful. 
Ostracoda were not so common in the loch itself as they were around its 
margin, particularly those parts that were more or less overgrown 
with vegetation, as round the north-east shore. Seventeen species of 
Ostracoda were obtained along this part of the shore; twelve species 
were obtained from the south shore, and only eight from the loch itself. 
Among the Cladocera the rare and interesting Leptoclora hyalina 
occurred in considerable numbers; Monospilus teiiuirostris was also 
frequent in the material collected at one or two places. The following 
were the common species: — Gammarus pulex, Diaptomus gracilis, 
Cypria serena, G . oj^htlialmica, Liimiicy there sancti-patrici, Daplinia 
lacustris, Pleiiroims trigonellus, Cliydorus sjdicericus. 
The larvae of insects were abundant in the loch, especially the larvae 
of the Iphemeridae. The Libellulidae and Phryganidae were also repre- 
sented in the larval stage more or less frequently. Some idea may be 
formed of the myriads of these organisms present in the loch when it is 
stated that a conspicuous ridge composed of cast-off skins of insect larvae, 
which had been washed ashore during the preceding stormy weather, 
extended along the margin of the loch for a considerable distance . The 
curious so-called water-bears (Tardigrada), now included in the 
class Arachnida, were common among the decaying vegetable matter at 
the bottom. Species of Notonectidae or water-bugs,” and of aquatic 
Coleoptera were also more or less common, though their distribution 
seemed to be more localised. 
The worms were represented by several species — parasitic and non- 
parasitic. Among the former were Schistocephahis solidus, obtained 
from the body-cavity of a Stickleback {G aster osteus aculeatus), and a 
species of tape-worm {Botlirioceplialus latus?), several of which were 
found in the alimentary canal of the trout, six specimens being taken 
from one fish. The heads of the parasites were fixed at the extreme 
end of the cceca or blind tubes of the stomach, and their bodies were 
so elongated as to extend well down into the intestine. Uusally one 
parasite occupied a caecum. Tuhifex rivulorum was very common in the 
loch. 
Phizopoda were common all over the loch. Several forms were 
obtained in the dredged and hand-netted material; the more typical 
varieties observed were: — Difflugia pyriformis, D. globular is (much 
less frequent than the first named), D. corona (appeared scarce), D. 
marsupiformis (of frequent occurrence). Diatomacea were abundant, 
especially in the deeper parts of the loch, and included a considerable 
number of species. 
Mr. Scott visited Loch Leven again in September and December, 
1897, and in March and June, 1898, when he found that the free- 
swimming Entomostraca, though very abundant, consisted mainly of 
the one species, Daphnia lacustris. Leptodora lujalina was moderately 
D 
