methods of plankton research. 539 



Results of the Plankton Work and Its Aims. 



I propose now to discuss briefly some of the results 

 obtained by the quantitative method, and the present 

 position of the work. The first ideas came from Hensen's 

 investigation into the distribution of the eggs of the plaice 

 in Kiel Bay. These are planktonic eggs, which float as 

 long as the salt contents of the water does not sink below 

 1*78 per cent., and this is seldom the case in the West 

 Baltic. It became evident that these eggs extruded at 

 many spawning grounds, must necessarily distribute 

 themselves widely, and the longer they remain floating 

 the more movement will take place and the more equal 

 the distribution will become. On this equal distribution 

 of the plankton particular stress must be laid, because 

 it forms the foundation on which the value of the quanti- 

 tative work depends. The investigation of these fish eggs 

 led to notice being taken of the other planktonic 

 organisms, and, finally, Hensen says — " The sea has its 

 yearly production in animals and plants, just in the same 

 way as a garden or field. For the land, it is an almost 

 impossible problem to work out this production, because 

 even if one, with extreme weariness, worked out the fauna 

 and flora completely and quantitatively for a small area, 

 at a short distance from this point the conditions and 

 distribution would be altogether different, and we could 

 never be certain that what was found in the small area 

 would be a true sample for a large area. In the sea the 

 conditions are quite different, the species and number 

 remain to a certain extent everywhere constant." 



Thus, with two fundamental hypotheses the quanti- 

 tative method has been applied. These are, first, that 

 the plankton organisms are equally distributed in the sea 

 where like conditions of existence are found ; and, second, 



