178 
typical character is corroborative of the view, though not conclusive, 
that we are dealing with a single species and not with several. 
This species has not been widely reported in the fresh-water 
plankton. It is evidently a planktont of warmer waters, and for 
that reason may have escaped notice, since the cooler waters have 
been the more thoroughly explored. Thus it was not found by 
Weber (’98) in Swiss waters in his thorough explorations about 
Geneva, nor by Jennings ('94, 96, ’00) in the Great Lakes or inland 
waters of Michigan. It has, however, been recorded by Skorikow 
(97) in the plankton of the Udy River, in Russia, where it was 
exceeded in number by only two species of its genus, B. pala and 
B. angularis, ranking tenth in numbers among all the rotifers. His 
data of frequency from July to October suggest several recurrent 
pulses. It has likewise been found by Lauterborn (’98) in the 
plankton of the Rhine, where he classes it with the stenothermal 
planktonts. Zacharias (98) finds it in ponds near Leipzig, and it 
was originally described by v. Daday (’85) from Hungarian waters, 
and again noted there by Kertész (94). Fuller exploration of the 
summer plankton in warmer regions will doubtless extend the record 
of its range. 
Brachionus militaris Ehrbg.—Average number of females, 147; 
of eggs (carried), 98. In previous years the species was much more 
abundant, the averages in 1897 being 1,412 females and 523 eggs, and 
in 1896, 1,288 females and 576 eggs. This greater development in 
years prior to 1898 is evident in many of the Brachionde. 
The following table gives the dates of first and last records in 
each season, and the location, temperature, and amplitude of the 
pulses in the several years. 
This is evidently a summer planktont with well-defined limits. 
These limits appear much less evident in 1898 (Table I.) than in 
prior years. In 1896 and 1897, for example, the species is almost 
continuously present in the plankton from the time of its first 
appearance until the last record for the season. All of the records 
save two lie above 70°, and the average temperatures at which the 
pulses occur are all at or above 80°. Its optimum thus lies near 
the summer maximum. The lower limits are not definitely 
established owing to insufficient collections in periods of rise 
and decline, but they seem to lie near 70°, with small numbers 
lingering to 60°. 




