402 MR. W. WEST AND PROF, G. S. WEST ON THE 
and Melosira is completely absent. Rhizosolenia morsa is the only Diatom 
which was observed to become abundant, attaining its greatest maximum 
in October and November (temp. 10° and 8°3° С. respectively) near the close 
of the autumnal decline in temperature, with a second slight increase in 
A similar periodicity was exhibited by this species in 
March and April. 
Wastwater. 
Fic. 1. 
NOV. | DEC. | JAN. | РЕВ. | MAR. | APR. MAY | JU. | JY. | IP 
1909. EN 
83 | 77*| 9:3 | 5-5°| 4° | 8:5* | 10° | 18:3 17° | E 
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ST. JACULIFERUM f. BIRADIATA A.TRIANGULARIS var. SUBTRIANGULARIS 
COS. ABBREVIATUM var PLANCTONICUM и. 
ARTHRODESMUS CRASSUS — — —— RHIZOSOLENIA MORSA +++++++++++ 
Chart of the periodicity of five of the most abundant constituents of the phytoplankton 
of Ennerdale Water. The temperatures are in degrees Centigrade. 
л / rar M 
Flagellates and Мухорһусе are rare in Ennerdale Water, although there 
is а small maximum of Lyngbya limnetica in October. 
Peridinium Willei only occurs from January to July, reaching its 
maximum in the latter month and then disappearing from the plankton. In 
