86 University of California Publications in Zoology [ Von. 14 
the oyster beds, are so few in number, and present such ineongruities, 
that they certainly do not furnish a fair comparison between the years 
in question. 
In the course of this survey, a few samples of nearly or quite fresh 
water were collected incidentally from streams tributary to San 
Francisco Bay. 
From Napa Creek, several miles above Mare Island, we obtained 
a single sample on April 1, 1912, at about high water. The salinity 
was found to be 5.62. From Suisun Bay, at station D-5961, a water 
sample was obtained on April 2, 1912, during the early flood tide. 
The chlorine permillage was 0.088. If this sample be regarded as 
diluted sea-water, the salinity equivalent, according to Knudsen’s 
tables, was 0.19 per mille, indicating the presence of rather more than 
one-half of one per cent of sea-water. 
Thanks to Mr. W. E. Allen, of the Stockton High School, we have 
had the opportunity of examining some samples of water from the 
San Joaquin River, at Stockton, California, taken during the months 
of January to July, 1913. Stockton is over thirty miles from the 
point at which the combined waters of the Sacramento and San 
Joaquin rivers discharge into Suisun Bay. The rise and fall of the 
tide are, however, pronounced there. 
As might have been expected, the proportion of chlorine was so 
low in these samples that it was necessary to concentrate the water by 
evaporation before making the titrations. The resulting figures differ 
so enormously from one another that we are at a loss for an explana- 
tion. The mean chlorine content of the eleven samples which were 
tested was 0.076 gm. per liter, while the figures ranged from 0.003 to 
0.169. It may be added that these two extremes represent samples 
taken during contiguous months. In fact, so little law is evident 
among these figures that we must reserve judgment as to their signif- 
icanece. Perhaps future studies of the river water at Stockton will 
render them intelligible. 
As in the case of our temperature data, it will be instructive to 
compare the salinity conditions in San Francisco Bay with those in 
certain other bodies of water where observations of this nature have 
been made. 
For Buzzard’s Bay and Vineyard Sound, the density ranged, 
during the observations made in the course of the biological survey 
of the Woods Hole Region (Sumner, Osburn, Cole and Davis, 1913) 
from 1.0212 to 1.0244, representing salinities of about 28.7 and 33.0 
