BIOLOGICAL STUDY OF CHESAPEAKE BAY WATERS 
327 
Among the Silicoflagellata identified by Cunningham are two well-known species 
Dictyocha fibula Ehr. and Distephanus speculum Haeck., both of which have been 
found in the waters about Woods Hole by Fish. 
During the October 1915 cruise, Dictyocha fibula was taken in comparatively 
large numbers for that species at area A (surface 160, 9 meters 360, 18 meters 80, 
27 meters 40, 36 meters 160, 46 meters 640), and somewhat less abundantly at area J 
close to the mouth of the Potomac River. North of that area it was found in verj 7 
small numbers. During the winter, spring, and summer cruises of 1916 (January, 
March, April, June, and July) specimens of this species were very scarce in the 
samples ; but in September of the same year there was an indication at area F of in- 
creasing numbers, and the counts for the October 1915 cruise were the largest obtained 
on any cruise. The data, although meager, indicate that this form has an autumnal 
maximum in Chesapeake Bay. 
The occurrence of Dictyocha fibula in considerable numbers at area A (salinity, 
approximately 25 to 27 per mille, temperature approximately 19° to 20° C.) and at 
area J (salinity, approximately 16 to 23 per mille, temperature approximately 18° 
to 19° C.) suggests that it is a neretic form as stated by Cleve (1897), although Gran 
has found it in mid-Atlantic ocean. 
Ceratium tripos (Muller), which is such an important element in the marine 
plankton and which has been found in abundance by Fish at Woods Hole and by 
Bigelow (1926) in the Gulf of Maine, has not been reported by Cunningham (1925) 
for the samples taken from Chesapeake Bay. The most abundant species listed for 
Chesapeake Bay was Ceratium jurca Ehr., while C. fusus Ehr. occurred in much 
smaller numbers. The data from the 1915-16 cruises of October, December, January, 
March, April, June, July, and September show the larger numbers during the latter 
half of the year and, as observed by investigators in other regions for Peridinians, 
after the spring maximum of the diatoms. During the cruise of July the highest 
counts for C. jurca were obtained, while during the cruises of the spring and early 
summer the numbers were small. The surface counts for area J, at the mouth of the 
Potomac River (and many other areas), show this relation clearly: October, 208; 
December, 1,320; January, 320; March, none; April, 80; June, 840; July, 23,400; 
and September, 200. 
As is the case of many diatoms the counts for the peridinian, Ceratium jurca in 
the neighborhood of the Potomac River were the highest obtained in the bay. As an 
example, during the July, 1916 cruise, the surface counts at areas distributed along 
the deep-water channel from the mouth of the bay to near Baltimore were the follow- 
ing: G, 800; A, 4,280; J, 23,400; L, 15,320; R, 1,360; and X, 120. Of these areas, 
J and L are close to the mouth of the Potomac River. 
While Ceratium jurca is known as a temperate oceanic form, widely distributed 
over the Atlantic Ocean and occurring sparingly in the Florida current according to 
Cleve (1898), it has been recorded in the Baltic, where the salinity was approximately 
from 15 to 17 per mille by Apstein (1906), in the saline bottom water (approximately 
17 to 20 per mille) entering Kieler Forde by Lohmann (1913), and in Fehmarn Belt, 
where the salinity was higher, by Buse (1915). Its presence in Chesapeake Bay then 
in comparatively large numbers near the mouth of the Potomac River is not surpris- 
ing even though the surface salinity was low, approximately 16 per mille at area J. 
Several species of the genus Peridinium were taken in Chesapeake Bay during 
the cruise of 1915 and 1916, |but no attempt to identify them was made. Rather 
