32 3 
BULLETIN OF THE BUREAU OF FISHERIES 
there has been a widespread tendency to regard the amounts of certain chemical com- 
pounds in the sea water as very important, if not the most important, factors deter- 
mining distribution and abundance. 
The early analysis of sea water for nitrates by Brandt (1899, 1902, 1920) and for 
phosphates by Raben (1905, 1910, 1914, 1920) which resulted in their emphasizing 
the importance of these compounds for the growth of the phytoplankton; the observa- 
tions of Nathansohn (1906) stressing the importance of the sinking nutrient material 
in the Mediterranean; the observations of the same author (1911) at Monaco, where 
a diatom increase was found following wet weather; Mathews’ (1918) analyses for 
phosphorus in the surface water of Plymouth Sound; the work of Allen and Nelson 
(1910) and Allen (1914) pointing out the importance of nitrates and phosphates for 
the growth of diatoms and the necessity of culture experiments in determining the 
number of diatoms in a certain quantity of water— all indicate an important relation- 
ship between the chemical compounds in the water and the distribution and abun- 
dance of diatoms. 
Recently, using newer and more accurate methods for the analysis of nitrates 
and phosphates, Atkins (1923, 1926) and Harvey (1926) have again found a close 
relation between diatom increase and dissolved phosphates and nitrates in English 
sea waters. Gaarder and Gran’s (1927) cultural work in Oslo Fjord on the growth of 
diatoms under variations in temperature, illumination, and nutrient salts and Gran’s 
(1929) investigation of the sea outside of Romasdalsfjord indicate the importance of 
these factors. 
The problem as to the factors that govern the distribution and abundance of 
diatoms is many sided and one in which it is difficult to study a single factor with the 
others under control. The efforts of Schreiber (1928) to devise such a procedure are 
worthy of special mention. Using single diatoms which had been rinsed by a special 
method so as to be free from all other organisms except supposedly a few bacteria, he 
determined the degree of intensity of light necessary for optimum reproduction, the 
quantity of nutrient materials and the temperature being kept constant. Such an 
approach as Schreiber has made, provided it is preceeded by a study of the organisms 
under natural conditions, it seems to me is very desirable. 
PROTOZOA 
The Protozoa occuring in the plankton samples of Chesapeake Bay were identi- 
fied, counted, and tabulated by Cunningham. They are listed and their distribution 
is discussed from certain points of view by Cunningham in the paper by Wolfe and 
Cunningham (1926). 
The fresh-water rhizopods were represented in the plankton by one or more species 
of Difflugia during the year 1916. Individuals of this form were present on all the 
cruises taken, and they were widely distributed. Difflugia is a bottom form, but one 
specie at least is known to form a gas vacuole and then to take on a tychopelagic 
existence (Steuer, 1910). Such a condition may account for their abundance in the 
plankton. Specimens of this rhizopod were taken in greatest numbers during the 
summer and fall cruises (July and September). The winter cruises yielded the 
smallest numbers. 
Another rhizopod found in the bay, but on one occasion only, was the oceanic 
plankton form Globigerina. 
