West: Phytoplankton of English Lake District. 135 



Desmids, and a large quantity of Peridiniiim Willei. The 

 Desmids included Penium truncatum, Micrasterias radiata, 

 Arthrodesmus triangularis var. subtriangularis , Hyalotheca 

 mucosa, H. neglecta, Stanrastrum Arctiscon, St. gracile var. 

 nanum, St. anatinum var. Lagerheimii, St. Ophinva. and St. 

 Brasiliense var. Liindellii. The two latter have not prexiously 

 been found in England. The principal Diatoms were Tabel- 

 laria fiocculosa, Eunotia pectinalis, and V anlieiirckia rhomhoide ■ 

 var. saxonica. A sterile species of Mongeotia was common, 

 and a curious anastomosis of two filaments was observed. The 

 connections between the filaments may have been the 

 result of aborted conjugation, and were cut off either completely 

 -or partially from the cells of the filaments (Fig, i a. and b.). 



The Rotifers Polyarthra platyptera, Amircea cochlearis, and 

 others, were frequent, and a number of specimens of JSIehela 

 flabellulum were observed. 



Fragments of Binudeara tatrana were fairly common in the 

 plankton. 



16. Stickle Tarn, Westmorland. May 1903. Altit. 1540 feet. 

 This is a mountain tarn about a quarter of a mile in length and 

 breadth, lying just under and to the eastward of Langdale Pikes 

 {2401 feet). The dominant feature of the plankton was 

 Peridinium Willei. Very few Desmids occurred, although 

 Staurastrum psendopelagicum deserves special mention, as it 

 was observed only from this lake, and from Windermere. 

 Diatoms (even Tabellarias) were few, and Dinobryon cylin- 

 dricum var. divergens existed in small quantity. Entomostraca 

 were in fair abundance, and much dark-brown organic matter 

 was present. Binudeara tatrana was again observed in the 

 plankton. 



17. Windermere. Altit. 130 feet. This is the largest of the 

 English lakes, ha\'ing a length of about loj miles, and a maxi- 

 mum breadth of about a mile. Average depth 78 feet ; maxi- 

 mum depth 219 feet. The lake is on the boundary between 

 Westmorland and the northern extremity of Lancashire. Its 

 margins are largely rock)-, with a good deal of woodland, but 

 the hills immediately around it are not very high. Its waters 

 are no doubt contaminated by the proximity of the villages of 

 Bowness and Ambleside. Material was collected from this lake 

 in June and September 1903, and periodical monthly collections 

 were made from September 1907 to August 1908. These are 

 considered in detail in a special part of this paper. 



1939 April I 



