120 МК, М. WEST AND PROF, G. S. WEST ON THE 
ИТ. August- November (autumnal fall in temperature). Cælospherium 
attains its maximum and dominates the plankton in August and 
September, after which it rapidly deereases in amount. Peridinium 
Willer disappears in the latter month. Slight maximum of some 
Desmids from September to November. 
Of the 16 species of Bacillariew, Synedra radians is common in October, 
‘Tabellaria jloeculosa and Asterionella. gracillima are both common in June, 
and Rhizosolenia morsa attains a considerable maximum in June and July. 
The latter has also a smaller maximum from December to February, dis- 
appearing entirely from the plankton from the end of February to the 
ibeginning of June. АП the other Diatoms are relatively rare. 
Of the Chlorophyceæ only the Desmids are of importance. A sterile 
„species of GZdogonium was common in the autumn, but all other Green Algæ 
«xcept Desmids are at all times comparatively scarce. The most abundant of 
the Desmids was Staurastrum paradowum and its vars. cingulum and 
Jongipes, but St. cuspidatum уат. maximum and Cosmarium abbreviatum var. 
planctonicum also occurred in great quantity in the warmer months. 
The Myxophyceæ were represented by 8 species, of which Colosplurrium 
Kiitzingianum alone occurred in great quantity. This Alga was never 
absent from the plankton, and at the time of its great maximum in August 
and September is the dominating constituent. As in the case of Loch 
Lomond, the colonies possessed the endophytic Aphanothece nidulans var. 
endophytica, Special attention should be called to a form of Lyngbya 
contorta, which occurred only in the cold period from December to April, and 
‘was most abundant in February. Merismopedia tenuissima was common in 
‘October. 
Of the flagellated organisms, Peridinium Wille? occurs in great abundance 
in June and July, but is entirely absent during the fall in temperature from 
‘October to February. 
6. осн EARN, PERTHSHIRE. 
This lake, whieh is situated at 317 feet above sea-level, is 7 miles in 
length and rather more than half a mile in breadth. The surrounding 
mountains vary from about 2000 feet to 3224 feet (Ben Voirlich), and the 
shores of the lake consist of gravel and drift. The area of the lake is 3°91 
square miles ; its main depth is 137°8 feet, and its greatest depth 287 fect. 
Owing to unforseen accidents collections were obtained from this lake only 
.on three occasions. 
Aug. 21st, 1908. Temp. of water 60° F. (=15°5° C.). Mixed plankton 
containing numerous Desmids and an abundance of Ceratium /irundinella. 
Staurastrum cuspidatum var. narimim was particularly common, and 
quantities of Ceælosphwrium were present. 
