156 
BULLETIN OF THE BUREAU OF FISHERIES 
and in the pond that was fertilized with inorganic fertilizer than in those ponds that 
were fertilized with organic fertilizer. 
The average number of all Crustacea, exclusive of nauplii, per liter of water was 
as follows: C 1, 484.41; C 2, 1812.21; C 3, 621.4; and C 4, 265.72. 
This brief summary of the zooplankton counts again shows quite definitely that 
the addition of fertilizer had a beneficial effect on plankton production. 
Centrifuge plankton . — The algse in the centrifuge plankton have been enumerated 
in all of the samples collected between June 27 and August 30, 1928. The results 
are tabulated in Tables 8 to 12. 
C 1 . Table 8 shows that Chroococcus was the only member of the Myxophycese 
that was present in large numbers. A maximum of 1,800,000 cells per liter occurred 
on August 30. Aphanizomenon was the only other blue-green alga that occurred 
in this pond. Among the Chlorophyceas (exclusive of the flagellates) Oocystis, Pedia- 
strum, Scenedesmus, and Staurastrum appeared in fairly large numbers. Oocystis 
reached a maximum on August 20, when 536,200 single cells and 960,000 colonies of 
this alga were present per liter of water. Pediastrum, Scenedesmus, and Staurastrum 
all reached a maximum on August 30. Of the flagellates, Pandorina and Pleodorina 
should be mentioned. These two colonial flagellates are the dominant forms in the 
plankton from July 28 to August 9. Pleodorina reaches a maximum of 960,000 
colonies per liter on July 28 and Pandorina a maximum of 749,800 colonies on August 
9. Eudorina and Volvox also occurred in the plankton, but only in small numbers. 
Stephanodiscus and Synedra were the only diatoms found in this pond and they 
occurred in small numbers only. 
C 2. Table 8 shows that Aphanizomenon and Chroococcus were the principal 
Myxophycese that occurred in this pond. Of these the former reached a maximum 
of 205,500,000 filaments per liter on June 27, the latter a maximum of 8,032,000 single 
cells and 9,728,000 colonies on August 30. A third blue-green, Anabaena, occurred 
once in considerable numbers. The principal Chlorophycese were Oocystis and 
Scenedesmus. Both of these algse attained a maximum on June 27, when each liter 
of water contained 240,000 single cells and 840,000 colonies of Oocystis and 8,550,000 
colonies of Scenedesmus. Other green algse present in appreciable numbers were 
Actinastrum, Closterium, Kirchneriella, Merismopedia, Pediastrum, and Tetrsedron. 
Synedra was the only diatom that was found. The plankton of this pond was charac- 
terized by the total absence of the flagellates that were so abundant in C 1. 
C 3. A comparison shows that the same algae that were most abundant in C 2 
are likewise the most abundant in C 3. Aphanizomenon reached a maximum of 
101,700,000 on July 19. In the case of Chroococcus the single cells were most 
abundant on June 27, whereas the palmella stage was most abundant on August 30. 
Of the Chlorophycese, Oocystis reached a maximum of 1,219,720 single cells and 
234,360 palmelloid colonies on August 30. The other leading green alga, Scenedesmus, 
attained a maximum of 3,840,000 colonies on June 27. It, however, was almost 
equally abundant on August 30. Other green algse that occurred in considerable 
numbers were Actinastrum and Pediastrum. As in C 2, Synedra was the only 
diatom that occurred in the plankton from this pond. It was present in large num- 
bers only once; namely, on June 27, when each liter of water contained 7,040,000 
cells of this alga. The colonial flagellates that were so abundant in C 1 were absent 
altogether from the plankton of this pond. 
