PLANKTONIC STUDIES. 633 



the biglier unit of the person or of the colony, which is composed of 

 many cells. If we actually wish to carry out exactly the method, held 

 by Ilensen as iudisi»ensable, of counting the individuals, and wish to 

 obtain useful results for his statistical work, then nothing remains ex- 

 cept a counting of all single cells which live in the sea. For onlj^ the 

 single cells, as the '' organic elementary individual," can form the 

 uatural arithmetical unit of such statistical calculations and the (com- 

 putations based thereon. If Heusen in his long " numerical protocols 

 and comparisons of captures" (9, pj). xi-xxxiii) places close to one 

 another as counted individuals — as coordinated categories — the uni- 

 cellular radiolaria, the corml of siphon o^jh ores and tunicates, the per- 

 sons of medusre, ctenophores, echinoderms, and Crustacea, the eggs 

 and persons of fishes, then he places together vastly incommensurable 

 bulks of quite different individual value. These can only be. compar- 

 able for his j)urpose if all single cells are counted. But since each fish 

 and each whale in the ocean daily destroys milliards of these planktonic 

 organisms, so, in order to gain an ''exact" insight into the "cj^cle of 

 matter in the sea," the cell milliards which compose the bodies of these 

 gigantic animals must be counted and placed in the I'eckoning. 



ECONOMIC YIELD OF THE OCEAN. 



Heusen holds the quantitative determinations of the plankton not 

 only as of the highest importance in theoretical interest to science, but 

 also in jiractical interest to national economy. He thinks '^ that we 

 will be able to invent correct modes of action in the interest of the 

 fisheries,* only if we are in position to form a judgment upon the pro- 

 ductive possibilities of the sea" (9, p. 2). Accordingly he regards it as 

 the most pressing i^roblem to determine the economic yield of the 

 ocean in the same way as the farmer determines the useful yield of his 

 fields and meadows, the yearly production of grass and grain. By the 

 counting of the planktonic individuals which Hensen has carried on for 

 a long time for a small part of the Baltic Sea, he thinks he has become 

 convinced that the "entire production of the Baltic in organic sub- 

 stance is only a little inferior to the yield of grass upon an equally 

 large area of meadow land." 



The farmer determines the yield of his meadows, garden, and field 

 by quantity and weight, not by counting the individuals. If instead 

 of this he wished to introduce Hensen's new exact method of deter- 



*^ How tlie practical interests of the iisheries can be advanced by quantitative 

 plankton .analysis I ain not able to understand. The most important modes of 

 action which we can employ for the increase of the fish production of the ocean — 

 artificial propagation, increase and protection of the fry, increase of their food 

 supply, destruction of the predaceous fislies, etc. — are entirely independent of the 

 numerical tables which Hensen's enumeration of individ(uils j;i ves. That the number 

 of swimming fish eggs furnishes no safe conclusion upon tin; number of mature fish 

 lias been pointed out above. 



