108 
BULLETIN OF THE BUREAU OF FISHERIES 
small bays, but this does not explain the conditions as they are often found. Since 
Woods Hole is a particularly unfortunate location to observe the factors of diatom 
production, I shall cite results obtained in Long Island Sound in 1922 and 1923. 
The first indication of local production was the variation in the species of 
pelagic diatoms found in the different harbors and river mouths along one shore. 
Had winds carried them there, one would expect to find the same species in all the 
harbors. This was not the case except diuring the greatest swarms, when the 
Sound seemed filled with a single species. In succeeding cruises it was noted that 
the volume of phytoplankton in the vertical hauls taken at the mouths of rivers and 
in harbors connected with inland streams was much greater than that of the mid- 
Sound or harbors containing no land outwash. Table 3 (p. 106) shows the centri- 
fuged volume, in cubic centimeters, taken with a Hensen medium-sized vertical net 
at various points in the Sound. The predominant species was STceletonema costatum. 
A strong west wind had prevailed for several days before the collections were made. 
Had the distribution of diatoms resulted from this they should have occurred 
most abundantly along the southeast shore near the eastern end. The table clearly 
shows that the greatest swarms occurred at the mouths of the rivers and harbors 
where the most land drainage is carried into the waters. The salinity is low in all 
parts of the Sound, and for that reason the diatoms do not penetrate far into the 
mouths of the rivers and harbors. No great tides sweep the Sound at any place 
except at the "race," and even there Galtsoff found that 8 miles is the maximum 
distance that the water is carried in a single tide. 
Another source of evidence can be found in Peck's (1896) report on diatom 
collections in Buzzards Bay. His stations were laid in two lines, one at right 
angles to the other, extending the length and width of the bay. A series of observa- 
tions at various points along these courses showed that the greatest abundance of 
diatoms occvured at the two inshore stations. The other two ends of the com-ses 
were located in Vineyard Sound and the rapids at Woods Hole, and therefore are 
not considered. He concluded from these records that there was a shallow area of 
diatoms surrounding all the shores of Buzzards Bay. A glance at Figure 12 wiU 
show that the two inshore points he selected (indicated by A) were near the 
mouths of the greatest harbors of the entire Bay. The large rivers at the head of the 
Bay empty their waters near Peck's north station, while the waters of the Acushnet 
and Nasketucket Rivers join at the point of his western station. Undoubtedly 
Peck would have found his hauls less rich if he had selected spots along the eastern 
shore. 
A noticeable characteristic of neritic plankton flora is the variety of diatoms 
that is usually foimd in every swarm. One or two species predominate, but the 
many other species occurring in smaller numbers make up the so-called "diatom 
society." Allen, in 1920, made the following statement: 
Detailed study of the records has clearly shown the important fact that when there is an 
increased production of the most prominent forms there is also increased production of the less 
prominent forms and an increase in the number of different forms. Such facts naturally lead to 
the assumption that conditions favorable to high productivity of diatoms in the sea affect a large 
number of forms in the same way. They also lead to the inference that determination of the 
species that shall lead in production is due largely to the biological factors, such as rapid multi- 
plication and vigorous development. 
