of the Fishery Board for Scotland. 287 



its upper end, the dredge being also used at several places. Copepoda — 

 chiefly Bias longiremus — were moderately common in the tow-net material, 

 both surface and bottom, and Cyclops equorus was frequent in the dredged 

 material. The Lamellibranch mollusc, Mya arenaria, was abundant in all 

 stages of growth, from an almost microscopic size up to about 1^ 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 have a dense growth of alga? 

 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 

 withyoungJ/^ce. Hydrobia ulvce 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-hsh.es occur in Loch Stenness. 

 It would be interesting to have this loch examined at certain intervals, as, 

 for instance, about or shortly after the time of spring-tides, and about the 

 time of low neap-tides, because from 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, both 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 1012*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 

 ston, 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 Ness. I had 

 the previous year partially examined the lower end in the vicinity of the 

 Bridge of Brosjar. 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 during 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. ; (b) 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 : — 



