70 JoUKISrAL OF THE MiTCHELL SoCIETY [Se ptfjilhcr 



Sherman, Franklin Williams, L. P. 



*Seymour, Mary F. Wilson, H. V. 



Shore, C. A. *Wilson, R. N. 



Spencer, H. Withers, W. A. 



*Strong, Cora . Winters, R. Y. 



ftTotten, H. R. *Wolf, F. A. 



Venable, F. P. *Wolfe, J. J. 

 *Wheeler, A. S. 



The following" papers were then presented : 



Some Methods and Results of a Planhton Investigation of Chesapeake 

 Bay. J. J. Wolfe and Beet Cunningham. 



The material was collected by the U. S. Ship Fishhawh at definite 

 areas in the bay between October, 1915, and September, 1916, The 

 methods of collection, preservation, volume determination, and count- 

 ing were discussed. In determining the volume, the centrifuge was 

 used on an original collection of 250 cc. Organisms in 25 cc. were 

 counted. 



The following conclusions were drawn : ( 1 ) There is little or no 

 relation between the volume of the precipitate and the number of 

 organisms. (2) Volume increases with depth. (3) Great varia- 

 tions in number of organisms occur in surface collections made on the 

 same day, probably due to tidal influences. (4) The maximum of 

 organisms is found at about 27 meters. (5) The optimum tempera- 

 ture lies between 46 degrees and 55 degrees. (6) The number of 

 organisms increases greatly in two annual crests — spring and fall. 

 This is not due to a general increase of all species, but to very great 

 increase in one. 



Further Occurrence of Cross-Conjugation in Spirogyra. Beet Cun- 

 ningham. 

 The writer reports the occurrence of cross-conjugation in S. weheri 

 Keutz. This supplements a previous report of the occurrence in 



S. inflata. 



