THE PRECIPITATION OF CALCIUM CARBONATE IN THE SEA. 



511 



These samples, without previous dilution, were plated in Peptone 

 Agar, 1 c.c. of the sample being used for each plate. The Agar was 

 cooled to just under 40° C. before plating. It is very necessary that 

 this temperature should not be exceeded, as many marine bacteria are 

 very sensitive to heat : the use of Agar at as high a temperature as 45° 

 C. will cause the death of a large proportion of the bacteria, though in 

 the process of plating they can only be exposed to this temperature for 

 a very short time. The cultures were kept in the dark at the room 

 temperature (averaging about 28' C), and at the end of 24 hours a 

 free growth of colonies was apparent. At the end of 48 hours the 

 plates were counted with the following results : — 



Depth. 

 Bottom (822 fathoms) 



600 fathoms 

 400 fathoms 



200 fathoms 

 >> >) 



100 fathoms 



50 fathoms 

 >> }} 



10 fathoms 

 )> >> 



Surface 



Number of colonies developing from 1 c.c. 

 of sample. 



171 



Ui 



15| 



16/ 



Very much overcrowded, indica- 



17 60 J tions of presence of many more 

 1500 I colonies which have not deve 

 I owing to overcrowding. 



uncountable owing to overcrowding. 



uncountable 

 }} 



uncountable 

 )> 



uncountable 



From these counts it is apparent that the number of bacteria falls 

 off at some point between 200 and 400 fathoms. 



The second station was worked on May 11th, at a point 14 miles 

 due east of Golding Cay. The sea was calm at first, and the wind 

 E.N.E., force 1, but later in the day a heavy swell set in and the 

 wind freshened to about force 4; eventually the weather became 

 so bad that it was impossible to work, and the station had to be 

 abandoned before it was completed. Bottom was sounded at 890 



NEW SERIES. — VOL. IX. NO. 4. MaKCH, 1913. 



2L 



