West: Phytoplankton of English Lake Dis^trict. 135 



Desmids, and a large quantity of Peridinium Willei. The 

 Desmids included Penium truncatum, Micrasterias radiata, 

 Arthrodesmus triangularis var. suhtriang^ilaris , Hyalotheca 

 mucosa, H. neglecia, Staurastrum Arctiscon, St. gracile var. 

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

 Brasiliense var. Lundellii. The two latter have not previously 

 been found in England. The principal Diatoms were Tahel- 

 laria flocculosa, Eunotia pectiyialis, and Vanheurckia rhomhoide ■ 

 var. saxonica. A sterile species of Mougeotia 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, Anurcea cochlearis, and 

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

 flahellulum were observed. 



Fragments of Binucleara tatrana were fairly common in the 

 plankton. 



16. Stickle Tarn, Westmorlaud. 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 pseudopelagicum deserves special mention, as it 

 was observed only from this lake, and from Windermere. 

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

 dricum var. divergens existed in small quantity. Entomostraca 

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

 was present. Binucleara tatrana was again observed in the 

 plankton. 



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

 English lakes, having 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 rocky, 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. 



1909 April I • 



