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in late summer and early autumn. It escapes through the silk net 

 readily, and no marked pulses in occurrence appear in the erratic 

 data of the filter-paper collections. It is found in the water-bloom, 

 and is predominantly a warm- water planktont. 



Euglena deses Ehrbg. Occurs occasionally in the plankton and 

 water-bloom during summer months. 



Euglena elongate Schew.* Average number in 1897, 278,970. 

 It is found irregularly in our plankton and water-bloom from July 

 to October. Originally described from New Zealand. 



Euglena oxyuris Schmarda.* Average number, 960,769. Next 

 to E. viridis this is the most abundant member of the genus in our 

 plankton. It is abundant during the summer, especially towards 

 its close during low-water conditions, when the water-bloom, 

 in whose formation it shares, is best developed. There is no 

 vernal development, and the fluctuations are but slight in com- 

 parison with those of most organisms of the plankton: There is a 

 slight indication of recurrent pulses at intervals of a few weeks. 

 Its optimum temperature lies near that of maximum summer 

 heat, that is, about 80, though some tendency to run over into 

 autumn months is manifest. 



Euglena sanguinea Ehrbg. There are only sporadic occurrences 

 of this species in the plankton. It is found along with E. vindis 

 among matted growths of Lemnacea, and on exposed and reeking 

 mud flats, where it forms patches of bright red color often of large 

 extent. It may be only a physiological condition of E. viridis, 

 with which it is always found. It has appeared in the plankton 

 most frequently in September, though found elsewhere throughout 

 the summer. 



Euglena spirogyra Ehrbg. Found but once in October, in the 

 river plankton. 



Euglena viridis Ehrbg.* Average number, 1,571,731 ; from silk 

 collections only 8,653. This is the most abundant of the larger 

 green flagellates in our plankton, and constitutes the greater part of 

 the water-bloom of summer months, when it forms towards four 

 p. m. a livid green scum on the immediate surface of the water. 

 Collections of the silk net give no clue to its abundance and shed no 

 light on its seasonal distribution. The filter-paper collections indi- 

 cate its presence from March to December, but in numbers only 

 during the warmer period, from May to October. There is no ver- 



