BIOLOGICAL STUDY OF CHESAPEAKE BAY WATERS 
349 
Acartia clausii has been recognized in Europe as a form which is able to flourish 
in abundance in water of low salinity such as is found in the Belt Sea, where the aver- 
age of 8 stations was 18.42 per mille, and in the mouth of the English Channel, where 
the average for 17 stations was 30.20 per mille (Farran, 1910, p. 77). One can not 
escape the conclusions that this copepod, as is shown by Wilson, may be found abun- 
dantly and in good condition in waters of even much lower salinity in Chesapeake 
Bay. As examples, the bottom net showed the following counts in round numbers 
during the March-April, 1921, cruise: Area Z, 75,000 (salinity <(12.42 per mille); 
V, 17,500 (salinity <9.17 per mille); T, 15,000 (salinity <11.51 per mille); S, 60,000 
(salinity <16.19 per mille); R', 2,900 (salinity <11.85 per mille); and R, 1,400 
(salinity <16.61 per mille). The specimens captured in the upper bay during this 
cruise can not be considered as only immigrants which had drifted in with the autum- 
nal and winter currents, for individuals were found at those same areas, although in 
smaller numbers, on all the other cruises. In addition, they were found at all areas 
visited, and these were very numerous and widely distributed. Acartia clausii was 
practically universal in occurrence over the bay and on all the cruises with the pos- 
sible exception of the one made in March-April, 1921. Even on this cruise the same 
would hold true, for the upper part of the bay (areas R, R', S, T, V, and Z) and very 
probably for the whole bay. Our data do not show higher surface counts for Acartia 
clausii in the region of the mouths of rivers ; nor can it be said that there were larger 
numbers on one side of the bay than the other, corresponding possibly to a difference 
in the degree of salinity. The data for the bottom samples are not suitable for such 
a comparison. 
The European records (Giesbrecht, 1892, p. 776; Scott, 1894, p. 68; Sars, 1903, 
p. 151, and Farran, 1910, p. 77) show that Acartia clausii is distributed in the cold 
and the warm water regions. While specimens of this species are found most abun- 
dantly in Chesapeake Bay during the colder months, considerable numbers are 
present at other times, and the records show that they may occur in waters which 
range in temperature from at least 4° C. to 27° C. 
CIRRIPEDIA 
Two species of barnacles have been brought to light from the offshore waters 
of Chesapeake Bay: Balanus improvisus Darwin and B. eburneus Gould. All of the 
specimens collected during the cruises of August, October, December, 1920, and 
January, 1921, were identified by Dr. H. A. Pilsbry at the request of the United States 
National Museum. 
The first species, Balanus improvisus, was taken by far the most frequently and 
was found distributed from the mouth of the bay to as far north as area S off James 
Island. It was collected from the following areas: G, G ' , F, G, D, A, Q, O, M, and 
N'. At the latter area, which is in the mouth of the Potomac River, the specimen 
obtained was living in water of a salinity that was not more than 13.96 per mille, 
while specimens at area G (in the mouth of the bay) were in water whose salinity was 
not more than 31.74 per mille. 
This form is given a wide distribution both by Darwin (1854) and by Gruvel 
(1905). The latter describes its distribution as along the English Channel, the 
coasts of France, Patagonia, Colombia, in the Rio de la Plata, and along the coast of 
the United States. It has also been reported from Nova Scotia. Sumner, Osburn, 
and Cole (1913, p. 130) point out that definite localities for its occurrence in the 
