144 G. HAROLD DREW. 



water. After hauling up, a little water was shaken from the neck, 

 and it was then sealed with the blow-pipe. By this method risk of 

 contamination from more superficial layers of water as the apparatus 

 is drawn up is avoided, since the changes in pressure and temperature 

 as it ascends tend to cause a continuous outflow througli the narrow 

 neck until the surface is reached. The samples were taken back to 

 the Laboratory, and cultures were made within three hours of col- 

 lecting. 



A somewhat similar apparatus was used for obtaining deep samples 

 from the station seventy miles west of Ushant, but the glass bulbs 

 were smaller and the tube leading from them was bent at riglit angles 

 to itself. Considerable difficulty was caused by the breaking of the 

 tube, owing to the force of the inrushing stream of water impinging 

 on the wall where it was bent at right angles. After collecting the 

 sample, the tubes were sealed with melted paraffin wax, and this 

 method does not appear to have caused any bacterial contamination 

 of the samples. Attempts to make Agar plate cultures in Petri 

 dishes on board did not give satisfactory results, as, owing to the 

 motion of the boat, the jelly set in irregular waves and lumps. Conse- 

 quently the samples were kept in ice, and cultures were made from 

 them at Plymouth twenty-four hours after collection. It is clear that 

 if in the future attempts are made to make plate cultures on board a 

 small boat, a very delicately swung table will be necessary, or else the 

 roll tube culture method must be employed. 



In Jamaica no apparatus for obtaining deep samples was available, 

 so the primitive method of lowering a sterilized stoppered bottle with 

 a string tied to the stopper was employed. At the required depth the 

 stopper was pulled out until the bottle was nearly full, and then 

 allowed to fall back in place. This method can only be used for very 

 slight depths, owing to the pressure of the water at greater depths 

 making it impossible to withdraw the stopper : a source of error also 

 is introduced in that the inrushing water passes in close proximity to 

 the stopper and its attachments, and may carry in bacteria which have 

 adhered to them when passing through the surface layers. 



The media most commonly employed for isolating the bacteria in 

 plate cultures had the following composition : — 



I. Peptoxe Agar. 



Peiitonc . . . . . 2'0 grainines. 



Potassium nitrate (KNO3) . . . 0'5 ,, 



Sea-water . . . .. 1000-0 c.c. 



A"ar Agar. . . . . 12*0 grammes 



