PLANKTO:VIC STUDIES, 607 



v.— COMPOSITION OF THE PLANKTON. 



The composition of the planlcton is in quccUtative as well as quantitative 

 relations very irregular, and the distribution of the same in place and 

 time in. the ocean also very unequal. These two axioms ap^ily to the 

 oceanic as well as to the neritic plankton. In both these important 

 axioms, which in my opinion must form the starting-point anil the 

 foundation for the cecology and chorology of the plankton , are 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 oi>posite oj)inion, " that in the ocean the plankton 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 exi)edition of Kiel, directed 

 by him, started on this '■'• purely theoretical view^'' and that it had '-'■full 

 results because this hypothesis was proven far more completely than 

 could have been hoped" (22, p. 24t).* 



These highly remarkable opinions of Hensen, contradictory to all 

 previous conceptions, demand the most thorough investigation; for if 

 they are true, tlien all naturalists who many years previously, and in 

 the most extensive compass, have studied the composition and distri- 

 bution of the plankton are completely in error and have arrived at 

 entirely false cx)nclusions. If, on the other hand, these propositions of 

 Plensen 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 plaidvton) are utterly worthless. 



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

 assumptions must be proved, " starting from a purely 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(3, 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 



■^ Heusen speaks of this in the following terms: "Hitherto it was the prevailing 

 A'iew that the inhabitants of the sea were distributed in schools, and that one, ac- 

 cordiug to luck and chance, according to wind, current, and season,' sometimes came 

 upon thick masses, sometimes upon uninhabited parts. Tliis in fact applies only in 

 a certain degree ior the harbors. For the open sea our knowledge teaches that nor- 

 mally regular distribution obtainstliere, which changes in thickness and ingredients 

 only withiu wide zones corresponding to the climatic conditions. I7i any case one 

 must seek the variation from su<;h condition according to the cause which has pro- 

 duced it, aud the occurrence of iueiinality is not to be taken as the given starting- 

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



