PROGRESS IX BIOLOGICAL IXQUIEIES, 1921. 29 



SUR^'ET OF CHESAPEAKE BAY. 



The biological and hydrographic survey of Chesapeake Ba}^ has 

 been continued by Dr. I^. P. Cowles, temporary investigator, during 

 the past year, and a large series of data on salinity, temperature, cur- 

 rent velocity, and current direction has been accumulated, together 

 with f|ualitative and quantitative collections of plankton, bottom 

 samples, and many specimens of the larger animals and plants. The 

 observations made and samples collected have not been confined 

 merely to the surface nor to tlie bottom but have been obtained at 

 definite depths, equal intervjils apart, from the surface to the bottom. 

 Probably the most valuable characteristic of the work is the fact that 

 the observations have been made about every sixth week during the 

 year at fixed stations arranged in lines across the bay, these lines be- 

 ing so placed as to adequately cover the bay from the region of Bal- 

 timore to the Capes. The Fisheries steamer Fhh Ilmck has been 

 €mployed in the work on the bay. 



During the year preliminary work has been undertaken to deter- 

 mine the hydrogen ion concentration of the sea water by colorimetry. 

 This method has now been perfected, and the tests made on the so- 

 called 24-h()ur stations, where observations are taken ever}^ 1^ hours 

 at definite intervals from the surface to the bottom for a period of 

 24 hours, have shown some very interesting conditions. 



The coming j-ear will be devoted to working over the data and 

 material, with possibly an occasional cruise on the bay to collect in- 

 formation that may be lacking. The general ])iirpose of the inves- 

 tigation is to gather and record the data that are necessary for the 

 interpretation of the seasonal and irregular movements of fishes, for 

 the s(/lutif)n of jiractical problems that arise from time to time 

 regarding fish and shellfish, and for the conservation and development 

 of the important fisheries of the bay. 



This general survey is being supplemented by a special investiga- 

 tion of fishes of the Chesapeake Bay. conducted by S. F. Ilildebrand 

 and W. C. Schroeder. While many fishes, especially the younger 

 exami)les of several species, liave been collected in connection with 

 the general survey, the supj)lemental field work on fishes was under- 

 taken only in the last months of the fiscal year. 



SURVEY OF SELECTED AREAS IX MlSSlSSim RIVER. 



In an investigation to deteiTnine the distribution of fresh-water 

 mussels. Dr. A. D. Howard made a somewhat detailed study of the 

 entire bottom in a portion of the Mississijij^i River, the area selected 

 being 3 miles in length and situated in Andalusia Chute, one of the 

 channels of the river in the vicinity of Fairport, Iowa. The river in 

 this section is comparatively straight and of rather uniform char- 

 acter as to gradient and depth, passing over soil of clay, sand, and 

 sedimentary rock (mostly limestone). 



The life on the bottom was found to have a rather definite dis- 

 tribution with reference to physiographic features of the river. Tn 

 general it was restricted to a zone 200 feet wide along each shore. 

 \Vhere islands occurred a narrower zone was found along the shores 

 of the islands. The distribution had apj)arently no particular rela- 

 tion to depth of water, iov the middle area of the stream (about 500 



