PLANKTON 245 



stations were so close together that the whole area investigated 

 measured only sixty-six miles by twenty-two, and his results 

 for the Chsetognatha (Sagitta, Plate XX, Fig. 2) show that 

 even at adjacent stations on successive days the numbers 

 obtained were very different, one catch being many times 

 another, and the greatest about thirty times as much as the 

 least. Now, if a vessel taking observations, say, twenty 

 miles apart, were to have traversed this area and obtained 

 only one of these gatherings, she might have gone off with 

 a so-called sample which was ten or twenty times too great 

 or too small to represent fairly the average, in either case 

 giving an indication that was false and might lead to entirely 

 erroneous conclusions. Similarly in the case of Doliolum, 

 Dr. Fowler found an enormous disproportion between the 

 amounts of the catch on the different days, even at closely 

 adjacent localities. It is obvious that if the number of 

 Doliolum present in the area were calculated from one of 

 his samples, the result would be entirely different from that 

 based upon other samples. Cases of this kind could be 

 multiplied, and have no doubt occurred in the experience 

 of most naturalists who have done much work at sea. 



The stock area of the open ocean, often quoted as being 

 under constant conditions, is the Sargasso Sea, far from 

 the disturbing influence of the coasts and isolated by a vast 

 surrounding current. There the conditions must be as 

 uniform as in any large oceanic area, and we would certainly 

 expect that there, if anywhere, the plankton would be 

 uniform. But in the twenty -four hauls made in the Sargasso 

 Sea during the Plankton Expedition the catches varied in 

 volume from 1*5 to 6-5 cubic centimetres. Where the 

 difference in range is so great as this, is one justified in taking 

 an average and using it to multiply up for the purpose of 

 estimating the population of the vast area ? 



Moreover, it is not justifiable to add together the estimated 

 amounts of the various possible sources of error and deduct 

 these from the apparent irregularity, as some of these 



