SOME PROBLEMS OF THE SEA. 11 



samples are not sufficiently representative, if your 

 observations are liable to be affected by any accidental 

 factor which, does not apply to the entire area, then your 

 results may be so erroneous as to be useless or worse than 

 useless, since they may lead to deceptive conclusions. 



Let us examine this assumed uniformity of the 

 plankton. It is a common experience of all 

 naturalists who have tow-netted much on the surface 

 of the sea, that many of the commonest organisms 

 occur in swarms, and that neighbouring areas 

 of water may differ very much in density of 

 population and may also change greatly from day 

 to day. Many such cases are recorded in the litera- 

 ture of biology, in the Reports of the " Challenger " 

 expedition, and elsewhere, but I may add here a few 

 observations of my own. On the West Coast of Scotland 

 I have seen large Copepoda so abundant for a mile or two 

 that they seemed from the deck of a yacht to be dancing 

 in crowds in the water. On stopping the boat and taking 

 a gathering with the net they were found to be Calanus 

 finmarchicus. In a few minutes we passed out of the 

 swarm. Consequently, two sample gatherings taken a 

 mile apart would, on this occasion, have given totally 

 different results. On our L.M.B.C. expeditions in the 

 Irish Sea we have on many occasions noticed and recorded 

 the very irregular distribution of Anomalocera pater soni. 

 On one occasion, in the North of Norway, I got in a short 

 haul of the surface tow-net a phenomenal amount of the 

 bright red northern form of Calanus finmarchicus— so 

 much, in fact, that after filling various jars, some of 

 which are still in our Museum, we cooked and ate the 

 remainder. We took tow-nettings in various other places 

 to the north and south, but never got another such haul. 



And this irregularity in distribution does not apply to 



