MICROPLANKTON 



253 



Table 18. Sample A of discoloured water near Sandwich Harbour. Collected at 13.45 nr - on 9 March 

 lg^o. Mixed, fractionized and diluted so that contents of 2-5 ml. could be counted direct, several counts 

 being summed. Factor to reduce numbers to cells/ml. x 0-4 



The area in optical section of the total organisms in 1 ml. of this sample, when spread over a Sedgwick-Rafter counting- 

 chamber, would thus be about 500 Whipple's International Standard Units, or o-2 parts per thousand, and their volume 

 some 1-5 parts per million of water. (The Sedgwick-Rafter cell, 5x2 cm. in area and with sides 1 mm. deep, holds 1 ml. of 

 fluid spread over an area of 10 cm. (= io 9 /x 2 ). One W.I.S.U. is a square 20 /x on one side (= 400 /r 2 ). One ml. = (io 12 /x 3 ).) 



Table 19. Sample B of discoloured zvater near Sandwich Harbour. First of two collected at 14.10 hr. on 

 9 March 1950. Noted as ' Khaki coloured water, reddish at a distance '. 1J8 of 10 ml. of the well-mixed 

 sample, i.e. of 0-55 ml., examined direct by drop method and counts summed. Factor to express results as 



17-2 



