PLANKTONIC STUDIES. 607 



v.— COMPOSITION OF THE PLANKTON. 



The composition of the plankton is in qualitative as well as quantitative 

 relations vcri/ irref/ular, and the distrihntion of the same in plaee and 

 time in the ocean also very unequal. These two axioms apply to the 

 oceanic as well as to tlie neritic i^lanktoii. In both these inix)ortant 

 axioms, wliich in my opinion must form the starting-point and the 

 fouudation for the avologi/ and chorology of the planJdo)i, arc embodied 

 the concordant fundamental conceptions of all those naturalists who 

 have hitherto studied carefully for a long time the natural history of 

 the pelagic fauna and flora. 



The surprise was general when Prof. Ilensen this year advanced an 

 entirely opposite oxDinion, " that in the ocean the i)lankton was dis- 

 tributed so equally that from a few hauls a correct estimate could be 

 made of the condition in a very much greater area of the sea" (22, p. 

 243). He says himself that the plankton expedition of Kiel, directed 

 by him, started on this ^^ purely theoretical view," and that it had ^^full 

 results because this hyj^othesis was i)i'oveu far more completely than 

 could have been hoped" (22, p. 244).* 



These highly remarkable opinions of Ilensen, contradictory to all 

 previous coiiceptions, demand the most thorough investigation ; for if 

 they are true, then all naturalists who many years j)reviously, and in 

 the most extensive compass, have studied the comj)osition and distri- 

 bution of the i)lankton are completely in error and have arrived at 

 entirely fiilse oxsnclusions. If, on the other hand, these propositions of 

 Ilenseu are false, then his entire plankton theory based thereon falls, 

 and all his painstaking computations (on which in the last six years he 

 has spent 17,000 hours, which he wishes to have number the individ- 

 uals distributed in the plankton) are utterly worthless. 



In the first place, the empirical basis upon which Ilensen founded his 

 assumptions must be proved, '^ starting from a jjurely theoretical point 

 of view. " The plankton expedition of Kiel was 9.) days at sea, and in 

 the months of late summer (July 15 to November 7) which, as is known, 

 offer m the northern hemisphere the most unfavorable time of all for 

 pelagic fishery (28, p. 1(), 18). Hensen himself says that it bore the 

 "character of a trial trip" (22, p. 10), and his companion Brandt names 

 it a "reconnaissance" upon which they had come to investigate rapidly 



" Hensen npeaks of this in the following terms: "Hitherto it was the prevailing 

 view that the inhabitants of th« sea Avere (listiibutod in scliools, and that one, ac- 

 cordiuj^ to luck und cliancc, according to wind, current, and season, sometimes came 

 uj^r)!) thick niasscs, sometimes upon uninhabited parts. This in fitct applies only iu 

 a certain degrees i'(»r tlic harbors. T'or the open sea our knowledge teaches that nor- 

 mally regular diHtribution obtains there, wliich changes in thickness and ingredients 

 only within wide zones eorrtispondin;;" to tiie. (dimatic conditions. In any case one 

 must seek theVariation from such condition according to the cause which has pro- 

 duced it, and the occurrence of ine((ua]ity is not to be taken as the given starting- 

 point for relative investigation" (22, p. 244). 



