PROGRESS IN BIOLOGICAL INQUIRIES 57 



region. Thirty-nine recoveries were reported, slioAvin<; a movement 

 of Avater eastward out of the sound and then south and west around 

 Nantucket. 



Other oceano<2:raphic observations in the way of serial tempera- 

 tures and horizontal and vertical tows were made from the Halcyon 

 and the Fish Haioh alono; the coast of Maine, in Massachusetts and 

 Cape Cod Bays, and on Nantucket Shoals. These were primarily a 

 part of the program of study of the spaAvning of cod and the sub- 

 sequent fate of the eggs and larval fishes. 



Arrangements have been completed to have extensive series of 

 temperatures taken at a number of carefully selected lightships 

 and lighthouses along the Atlantic coast. 



The Avork on the oceanographic surA'ey of Chesapeake Bay has 

 gone forAvard and the data are gradually being \)\\t into shape for 

 publication. 



ECOLOGY OF FRESH-AVATER LAKES 



The (luantitative studies of the flora and fauna of Green Lake, 

 Wis., Avere completed in 1924, and a report based upon the data ob- 

 tained in this investigation is now being prepared. Observations on 

 the plankton of Green Lake Avere begun on February 28, 1924, and 

 Avere continued until November 8. The organic matter in the centri- 

 fuge plankton reached a maximum of 1,370 milligrams per cubic 

 meter of water on April 30, and then declined to a minimum of 542 

 milligrams per cubic meter on July 3. The quantity rose to 660 

 milligrams on July 30 and to 1,179 milligrams on September 3, then 

 fell to 912 milligrams on October 11 and rose to 1,131 milligrams 

 per cubic meter on NoA^ember 8. 



During the month of July a special study of the number and dis- 

 tribution of the shrimplike crustacean, Mysis relicfa, was made. In 

 summer this animal is A'ery generally distributed over the bottom of 

 Green Lake, where the Avater reaches a depth of 12 meters or more. 

 It is most abundant, however, over certain tjqDes of bottom, such as 

 sand, graA-el, or marl that is kept free of mud by the action of cur- 

 rents. As many as l,10o incliA^iduals were obtained in one haul of the 

 dredge off Sandstone Bluff, for example, Avhile hauls OA'er mud bot- 

 tom yielded relatiAcly small numbers. This animal forms an im- 

 portant item in the food of the ciscoes, and enough material was ob- 

 tained for a food analysis. 



During the month of August 50 lakes in northern Wisconsin were 

 visited for the purpose of making temperature, hydrogen-ion, and 

 plankton observations. These northern lakes haA^e a someAvhat loAver 

 temperature and less calcium and magnesium in solution ; some of 

 them, in fact, have A'ery soft water, containing only 1 to 2 cubic 

 centimeters of fixed carbon dioxide per liter of Avater. The chief 

 purpose of the investigation Avas to determine Avhether these northern 

 lakes support as large a growth of plankton in summer as do the 

 lakes of southeastern Wisconsin, where the water is someAvhat warmer 

 and has a distinctly larger amount of calcium and magnesium in 

 solution. 



The hydrogen-ion concentration A^aried from pH 8.9 to 5.2 in the 

 northern lakes. In those haA'ing Aery soft Avater the surface Avas 



