36 



Papers from the Marine Biological Laboratory at Tortugas. 



The third station was worked on May 23 at a point 10 miles ENE.3^E. 

 of Golding Cay. The wind was east, of about force 4. As it had been 

 blowing for the previous ten days without intermission, the sea was so rough 

 that it was only possible to work when steaming slowly ahead into the wind. 

 This resulted in the production of a great deal of stray on the sounding- 

 wire, so that the number of fathoms of wire run out is greater than the 

 actual depth at which the samples were taken; these differences will be 

 large for the more superficial samples, but small at greater depths, as the 

 wire strays in a curve whose gradient becomes very steep a little below the 

 surface under these conditions. 



The following temperatures were recorded : 



At this point the station had to be abandoned, owing to the bad weather. 

 The samples down to i6o fathoms were diluted i in loo with sterilized sea- 

 water before plating in peptone agar; the remaining two were plated undi- 

 luted. At the end of 48 hours the following counts were made, representing 

 the mean of the number of colonies in the two plates made from each 

 sample : 



. ^, r • No. of colonies 



Length of wire developingfrom 



run out. jc.c. of sample. 



Fms. 



Surface is.ooo 



20 I 15. 500 



100 13,700 



160 13.300 



250 14.300 



350 16 



The colonies developing in all the cultures were only of two kinds, the 

 Bacterium calcis and the non-denitrifying species already described. The 

 non-denitrifying species formed a relatively small proportion of the total, 

 and were not found at all in cultures made from samples taken below 250 

 fathoms. As they appear to be comparatively inactive chemically, and 

 as nothing is at present known concerning the part played by them in the 

 metabolism of the sea, they will not be further considered here. 



A consideration of these results obtained in the Tongue of the Ocean 

 shows that the waters down to a depth of somewhere about 300 fathoms 

 in April 1912 contained an enormously larger number of bacteria than the 

 water in the neighborhood of Tortugas in June 191 1. The number of 

 bacteria falls off from about 14,000 to about 12 per i c.c. between depths of 

 250 and 350 fathoms; the temperature at 250 fathoms was about 15° C. 

 and at 350 fathoms about 11° C, and it was shown in June 191 1 at Tortugas 



