28 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Such Plankton gatherings taken continuously from 

 an ocean liner give, however, information only in regard 

 to the surface fauna and flora of the sea — including many 

 organisms of fundamental importance to man as the 

 immediate or the ultimate food of fishes and whales and 

 other useful animals. 



It was therefore a great advance in Planktology when 

 Professor Victor Hensen (1887) introduced his vertical, 

 quantitative nets (fig. G) which could be lowered down and 

 drawn up through any required zones of the water. The 

 highly original ideas and the ingenious methods of 

 Hensen and his colleagues of the Kiel School of 

 Planktology — whether all the conclusions which have 

 been drawn from their results be accepted or not — have 

 at the least inaugurated a new epoch in such oceano- 

 graphic work; and have inspired a large number of 

 disciples, critics and workers in most civilised countries, 

 with the result that the distribution of minute organisms 

 in the oceans and the fresh waters of the globe is now 

 much more fully known than was the case twenty, or even 

 ten, years ago. But perhaps the dominant feeling on the 

 part of those engaged in this work is that, notwithstanding 

 all this activity in research and the mass of published 

 literature to which it has given rise, much still remains to 

 be done, and that the Planktologist is still face to face 

 with some of the most important unsolved problems of 

 Biology. 



The fundamental ideas of Hensen were that the 

 Plankton, or assemblage of more or less minute drifting 

 organisms (both animals and plants) in the sea, is 

 uniformly distributed over an area where the physical 

 conditions are approximately the same, and that by taking 

 a comparatively small number of samples it would be 

 possible to calculate the quantity of Plankton contained 



