DEPARTMENT OF MARINE BIOLOGY. 



141 



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 results below. From these counts it is appar- 

 ent that the number of bacteria falls off at some point between 200 and 400 

 fathoms. 



Depth. 



Bottom {822 fathoms). 



600 fathoms 



400 fathoms 



Colonies 

 developing 

 from I c c. 

 of sample 



{ 



17 



15 

 16 



Depth. 



I 200 fathoms.., 



100 fathoms., 

 50 fathoms., 

 10 fathoms.. 



Surface 



Colonies 

 developing 



from I c.c. 

 of sample. 



r*i6o 



L*ioo 

 (t) 

 (t) 

 (t) 



* Very much overcrowded, indications of presence of many more colonies which have 



not been developed owing to overcrowding. 

 t Uncountable owing to overcrowding. 



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

 of Golding Cay. The sea was calm at first, and the wind ENE., force i, 

 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 fathoms, but there was some stray on the wire, so that the 

 true depth was probably about 825 fathoms as shown by the chart. The 

 bottom consisted of fine white calcareous ooze ; no pteropod but some globi- 

 gerina shells were seen. The following temperatures were recorded : 



Samples down to a depth of 200 fathoms were diluted i in 100 with ster- 

 ilized sea-water before plating. The following results were obtained after 

 48 hours' growth. The figures represent the mean of the number of colonies 

 developing in the two plates that were made from each sample. It is here 

 apparent that the number of bacteria per cubic centimeter falls oflf very 

 rapidly between 200 and 300 fathoms. 



The third station was worked on ]\Iay 23 at a point 10 miles EN'E.J4E. 

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



