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BULLETIN OF THE BUREAU OF FISHERIES 
fied species of the genus Tintinnopsis, although the other (Peridinium depressum) 
was also taken in great numbers. Hundreds of the thimblelike cups of Tintinnopsis 
could be seen at one time in the field of the microscope. Certain other forms were 
noticed at different periods throughout the year, but they never formed an im- 
portant part of the plankton. 
A second species of Peridinium {Peridinium oceanicum var. oUongum) had a 
maximum in the fall of both years. This is a much smaller form than P. depressum 
and was never present in such large numbers. In 1922 it appeared on July 9, 
reaching its maximum late in August and disappearing about Spetember 15. In 
1923, as in the case of almost all the planktonic forms of that season, the period was 
later, commencing about September 2 and remaining until November 20. 
Fig. 24.— Occurrence of most abundant forms of Protozoa in surface collections of 1923. , Ceratium tripos; , 
C. maCTOceros; ... , C. Jusus: . — , Peridinium depressum; ........... P. oceanicum var. oblongum; , 
Tintinnopsis sp 
During the fall maximum of Ceratium the water fairly blazed with light when 
disturbed. They caused the net to gleam like a lantern, and often bottom forms 
not normally taken at the surface were attracted to it. 
An interesting radiolarian {Heterophrys sol) also occurred in the fall. During 
September and October, 1922, the numbers gradually increased until they became 
exceedingly abundant, often being found in bunches of 20 or 30 specimens. Afterthe 
26th of October the number rapidly diminished until November 1, when the last 
one was seen. None appeared in the collections of 1923. 
Of the Silicoflagellata, DistepTianus speculum and Dictyocha fibula occurred as 
scattering individuals throughout the year except in the warmest months. Diste- 
phanus was most abimdant from November, 1922, to March, 1923, and Dictyocha 
appeared from September to May. Many Foraminifera appeared, usually after a 
storm. These, however, sank quickly to the bottom again and were rarely taken 
