70 
crease of bicoseca in the plankton, but is not in itself the primary 
cause for 1ts appearance in the plankton. 
Carteria multifiis (Fres.) Dill.*—Average number, 2,365,384. 
In 1897 more than one hundred-fold as abundant. This species was 
recognized only in the autumnal and hiemal planktons, from 
August till January in 1897-98 and from October to February in 
1898-99. It is not easily and with certainty identified by the 
usual methods of plankton counting, and probably other species of 
similar habitus may have been included to some extent; and, on the 
other hand, many Carteria.may have been thrown with the “un- 
identified” flagellates, especially in earlier years. This species 
occurs throughout the whole range of temperatures, and its maxi- 
mum development (6,476,400,000) was attained October 5, 1897, at 
70°. A pulse prior to this appeared September 7, at 2,846,250,000. 
From the major pulse in October there is a gradual decline as the 
minimum temperatures are reached. 
The remarkable outbreak of Carteria in the autumn of 1897 was 
associated with unusually low water (Pt. I., Pl. XI.) and concen- 
tration of sewage and decrease in current. The water of the stream 
was of a livid greenish-yellow tinge, due principally to great numbers 
of Carteria, which developed to the exclusion or diminution of other 
chlorophyll-bearing flagellates such as Euglena, and of diatoms such 
as Melosira. This unusual development seems to have been a dis- 
turbing factor in the usual seasonal routine of the autumnal plank- 
ton of that year. <3 
The distribution of Carteria in the river was remarkable. It 
formed great bands or streaks visible near the surface, or masses 
which in form simulated cloud effects. The distribution was 
plainly uneven, giving a banded or mottled appearance to the 
stream. The bands, 10 to 50 meters in width, ran with the channel 
or current, and their position and form were plainly influenced by 
these factors. No cause was apparent for the mottled regions. 
This phenomenon stands in somewhat sharp contrast to the distri- 
bution of the usual water-bloom upon the river, which is generally 
composed largely of Euglena. This presents a much more uniform 
distribution, and unlike the Carteria is plainly visible only when it 
is accumulated as a superficial scum or film. Carteria was present 
in such quantity that its distribution was evident at lower levels 
so far as the turbidity would permit it to be seen. It afforded a 
