VALIDITY OF ANALYSES 33 



Small Calanoids 

 The numbers estimated from the sub-sampling of the St. 121 sample were as follows: 

 Sub-samples 1/40 of whole sample 



i/S° 

 1/60 



1/100 

 giving a mean of 3071. 



Six out of these twelve sub-samples give a range of variation from this mean of 

 from — 12 to + 15 per cent. 



Nine out of these twelve sub-samples give a range of variation from this mean of 

 from — 15 to + 25 per cent. 



The twelve sub-samples give a range of variation from this mean of from — 21 to 

 + 43 per cent. 



In routine practice when taking a sub-sample with the pipette one is generally able 

 to tell when one has taken a sub-sample which is giving an exceptionally high or low 

 result, and the pipette is then emptied and another sub-sample taken. 



The sub-sampling of the St. 41 D sample gave similar results: 

 Sub-samples 1/40 of whole sample 



1/60 



giving a mean of 810. 



Six out of these twelve sub-samples give a range of variation from this mean of 

 from — 12 to + 13 per cent. 



Nine out of these twelve sub-samples give a range of variation from this mean of 

 from — 18 to + 13 per cent. 



The twelve sub-samples give a range of variation from this mean of from — 25 to 

 + 27 per cent. 



Whilst no doubt over the whole survey somewhat larger variations will occasionally 

 occur we may take it that in the majority of instances the error will not exceed 25 per 

 cent. 



Medium Calanoids 

 The numbers estimated from the sub-sampling of the St. 121 sample were as follows: 



Sub-samples 1/40 of whole sample 1840 2080 1520 



1/50 ,, ,, 2600 2700 2000 



1/60 „ „ 3000 1800 i860 



1/100 „ „ 2600 1300 1400 



giving a mean of 2058. 



