552 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



variations in the quantity and constitution of the catches 



at two stations where apparently the conditions prevailing 

 were the same. Hensen and the later German workers 

 regard these fluctuations that occur as of little import- 

 ance; but it is clear that more knowledge upon this 

 question of the unequal distribution is required, because 

 if small samples (and they are only 15 c.cm. for 

 the centrifuge) are to be taken, they will give no 

 true picture of the plankton present in either quantity 

 or quality, nor of the relations of larvae to adults, if 

 swarms occur or if there is unequal distribution to any 

 considerable extent. It is, therefore, very necessary to 

 take a small region and to make sure that the hydro- 

 graphical and other conditions are the same throughout, 

 or to take catches in exactly the same way, side by side, 

 or separated by the length of a vessel, in order, after a 

 systematic research, to tabulate the fluctuations that have 

 occurred. Herdman (17), who is working on these lines 

 at Port Erin, has already given some surprising figures 

 of the variations in the catch of two nets worked side by 

 side, and the detailed account of his results, to be 

 published in this volume (see 19) should throw some light 

 on this very important question. 



