of the Fishery Board for Scotland. 
287 
its upper end, the dredge being also used at several places. Copepoda — 
chieHy Dias longiremus — were moderately common in the tow-net material, 
both surface and bottom, and Cyclops eqnorus was frequent in tlie dredged 
material. The Lamellibranch mollusc, Mya arenaria, was abundant in all 
sta.ues of growth, from an almost microscopic size up to about inch, 
in breadth, but no adult specimens were obtained, the reason no doubt 
being that the dredge could not penetrate deep enough into the mud to 
capture them, for where the conditions are favourable they burrow to a 
considerable depth. The bottom appeared to liave a dense growth of algse 
covering it in many places, for the dredge, on being hauled up on several 
occasions, was filled with little else than growing weed, which was crowded 
with young i/yce. Hydrobia tdvce was also present in considerable numbers. 
The weed referred to evidently shelters a numerous micro-fauna, and there- 
fore forms a rich feeding-ground for the various fishes inhabiting the loch. 
It is reported that at least 12 kinds of food-tishes occur in Loch Stenness. 
It would be interesting to have this loch examined at certain intervals, a^^, 
for instance, about or shortly after the tims of spring-tides, and about the 
time of low neap-tides, because froQi its peculiar position the salinity of 
the water must vary considerably, and the varying condition of the water 
will no doubt react to some extent on the fauna, bath vertebrate and 
invertebrate. The loch is of no great depth, the deepest part dredged 
by us being little over 5 fathoms. The following physical observations 
were taken : (a) near the upper end of the loch, density 101 2 '7, tempera- 
ture of water when density was taken 11-2 C; (b) near lower end, density 
1012*6, temperature 11 '5 C, which shows that the water was decidedly 
brackish at the time of our visit. 
Loch Harray. 
This loch was visited on September the 30th, and was examined by 
means of a rowing-boat, kindly placed at my service by Mr John John 
eton, of Vetquoy, near the head of the loch. I tow-netted and dredged 
from the upper end of the loch down as far as Tenstone ISTess. I had 
the previous year partially examined the lower end in the vicinity of the 
Bridge of Brogar. The microfauna of this loch showed a marked contrast 
to that of Loch Stenness ; I did not obtain a single Cladoceran in Loch 
Stenness, but here they were in myriads, almost to the exclusion of every- 
thing else, the prevailing form being Daphnia longispina (?). Copepoda were 
also present, and in the vicinity of Tenstone Ness Cypria serena likewise 
occurred in the tow-net collections ; but neither were very plentiful. 
Loch Harray is very shallow, the deepest part, I was informed, being 
little over 2 fathoms. I found the bottom to be very rough and stony, 
with occasional intervening patches of clean ground which consisted of 
fine blackish mud or muddy sand ; the bottom is said to be very uneven, 
and this was partly borne out by what was observed by us daring our 
examination. Pond-weed, water-milfoil, and other plants were of frequent 
occurrence in the loch, some of the plants having stems 6 to 7 feet in 
length. At the time of our visit the water was nearly though not quite 
fresh, as the following density observations show. Thus (a) near the head 
of the loch, density 1001-3, temperature of water at the time the density 
was taken 8*5 C. ; (6) off Tenstone Ness (near the middle of the loch), den- 
sity 1001*6, temperature 8*6 C. For comparison it may be stated that the 
water from a pump-well at Stromness had a density of 1000*4, temperature 
14*7 C. 
The following are the lists of invertebrata obtained in the two 
lochs : — 
