344 THE FRESH- WATER LOCHS OF SCOTLAND 
are thick and brown, but not stumpy like those of the Orkney Islands. 
The adults have large eyes, they bear five or even as many as nine 
summer eggs, and the total length, including the spine, is about 2 "8 mm. 
In general, it seems to be most nearly allied to the var. rosea, Sars, 
but differs in the absence of coloration. In several lochs males were 
abundant ; they looked very like the younger females, and the spine 
was not at all reduced. Males were taken in Loch Spiggie, 4th July 
1903; Loch Littlester, 7th August 1903; Loch Cliff, 4th August 1903; 
Loch Clousta, 12th July 1903 ; and Loch Vaara, 13th July 1903 ; 
ephippia were seen in Loch Littlester. 
As regards the formation of ephippia and the occurrence of males, 
these seem to be rather uncommon phenomena in the Scottish lakes 
during the autumn months. They have been seen in the five Shetland 
lochs above mentioned, 4th July to 7th August 1903; in Loch Baile sC 
Ghobhainn, 13th August 1904 ; in Loch Ness, 29th August 1903, also 
6th October 1898; in Loch Oich, 7th October 1898; in Loch a^ 
Mhuilinn, near Fort Augustus, 27th August 1903; in Loch an 
Lagain, 2oth September 1902; in Loch an Tuirc, 14th September 
1902; in Loch Maol sC Choire, 13th September 1902; in Loch More 
(Caithness), October 1903 ; in Loch Harray, 22nd August 1903 ; and 
in Loch Fadagoa, 9th August 1903 ; but as these few records are all 
we know of from some hundreds of lochs examined during the summer 
and autumn months, we must suppose that, if ephippial formation 
is a normal function in the life-history of a Daphnia, it must take 
place in the winter months, and in fact Mr T. Scott found them 
frequently in December. 
In the lochs of Shetland, then, they occur several months earlier. 
So far as our records go, ephippial formation never occurs in the 
lakes of the Highland region earlier than August ; but, curiously 
enough, ephippium-bearing Daphnias were taken in Edgelaw Reservoir 
(near Edinburgh) as early as 7th July 1903, and, according to Mr 
Scott, in Duddingston Loch (Edinburgh) on 15th June 1898, in which 
loch also they were found on 16th September 1898 and also on 15th 
December 1897, and in Forfar Loch on 16th June 1898, and again 
on 15th September 1898. 
But the lochs just mentioned are of small size, and being com- 
paratively shallow the plankton fauna is subject to the extremes of 
temperature conditions and perhaps even to partial desiccation ; in 
such an environment the ephippial function becomes more important 
than in the large lochs where more uniform conditions prevail. 
Bosmina ohtusirostris, Sars. — The plankton Bosmina in all the 
areas belonged to the species B. ohtusirostris, Sars ; in no case have 
I met with B. longirostr'is, and only once B. longispina, Fr. Leydig. 
The Bosmina obtusirostris varied somewhat in size and general 
