81 
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 1n the plankton and 
water-bloom during summer months. 
Euglena elongata 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 oxyurts Schmarda.*—Average number, 960,769. Next 
to E. viridis this 1s 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. viridis 
among matted growths of Lemnacee@, 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 EF. 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 Ehrbe.*—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- 
