226 



Papers from the Department of Marine Biology. 



In table 7 are given the determinations made on board, during the 

 return from Tortugas to New York, together with the latitude and 

 longitude of the stations. 



Table 7. 



^Inside Marquesas Lagoon. 



2Key West. 



In figure 3 the stations from Key West to New York are marked by 

 crosses and the appended numbers indicate the number of cubic centi- 

 meters of O2 per liter. The track of the steamer during the night is 

 marked by a black line and the track during the day is unmarked. 

 Since the steamer had a speed through the water of about 12 knots, 

 actual diurnal variations could not be determined. If, however, we 

 assume that the Gulf Stream arises from a source of uniform composi- 

 tion, those observations in the axis of the stream should show the diur- 

 nal variations, except for the modifications due to local meteorological 

 differences. Although Trichosphcerimn and other phytoplankton were 

 present, and photosynthesis can occur at all depths less than 300 

 meters (light penetrating 1,000 meters), no marked or certain increase 

 in O2 in the sunshine was noted. At 5''20°' a. m. August 2 there were 

 4.47 c.c. O2 per Uter and at 3 p. m. August 1 there was 4.50 c.c; but 

 no other pair of observations in the Gulf Stream shows a greater O2 



