PLANKTONIC STUDIES. 631 



OCEANIC^ POPULATION — STATISTICS. 



Statistics iii general is known to be a very dano'erous science, be- 

 cause it is commonly employed to find from a number of incomplete 

 observations the ap[)roximate avei-age of a great many. Since the 

 results are given in uumbers, they arouse the deceptive appearauce 

 of mathematical accuracy. This is especially true of the complicated 

 biological and sociological conditions, whose total phenomenon is con- 

 ditioned by the cooperation of numerous different factors, and is, 

 therefore, very variable according to time and place. Such a highly 

 complicated condition, as I believe I have shown, is the composition of 

 the plankton. If, as Heusen actually wishes, this were to be sufficiently 

 analyzed by counting the individuals, and oceanic population statistics 

 were thereby to be made, then this would only be ]iossible by the forma- 

 tion of numerous statistical tables, which should give results in figures 

 of the plankton fishery quantitatively in at least a hundred different 

 parts of the ocean, and in each of these at least during ten different 

 l)eriods of the year. 



A single ^'reconnoitering voyage" on the ocean, a single "trial 

 trip," limited in time and place, like the three-months Atlantic voyage 

 of the N'ational expedition, can furnisli only a single contribution to 

 this subject. But it can in no way, as Brandt thinks, offer " firm foun- 

 dations" for the solution of this and that "thorough analysis" (23, p. 

 525). If, also, after six years the 120 catches should actually be counted 

 through (after a labor of more than 17,000 hours), if by statistical 

 ariangement of this numerical protocol, by rational reckoning of their 

 results, a serviceable conception of the quantity of individuals of the 

 oceanic region investigated should be obtained, then at best this one 

 computation would give us an fqjproximate conception of the conditions 

 of population of a very small part of the ocean ; but from it by no means 

 can Ave, as the investigator of Kiel wishes, arrive at conclusions bear- 

 ing upon the whole Oi'can; for that purpose hundreds of sijuilar com- 

 putations must be made, including the most diverse regions and based 

 uiion contin uous series of observations during whole years. The zo(iloo-- 

 ical stations would be the best observatories to carry out complete series 

 of ohservaiions o£ thifi character, not such trial trips as the tliree-mouths 

 voyage of the National. * 



* In my opinion the results of the XaUonal expedition of Kiel woiihl liavo been 

 ((uit-c ditVerent if it h;id benn carried out in the three months from Jannary to March, 

 instead of from .Inly to October. On the wliole, the volume of planktonic catcli, at 

 least in the North Atlajitic Ocean, wouhl have more tlian doubled; in some ]daces it 

 would have been increased many fold. Its constitntioiv would have be(!n eutirely 

 ditVerent. If the expedition had by accident fallen in with a /oucurrent, and its 

 voyage had continued in it for a few miles, the contents of the nets would have 

 certainly been a hnndreflfuld, jmssibly a thousandfold, greater. 



