PLANKTONIC STUDIES. 631 



OCEANIC POPT'LATION — STATISTICS. 



Statistics ia general is kuowti to be a very danoeroiis science, be- 

 canse it is commonly employed to lind from a number of incomplete 

 observations the approximate average of a great many. Since the 

 results are given in numbers, they arouse the deceptive api^earauee 

 of mathematical accuracy. This is especially true of the comi^licated 

 biological and sociological conditions, whose total x)henonu!non is con- 

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

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

 complicated condition, as 1 believe I have shown, is the composition of 

 the plankton. If, as Hensen actually wishes, this were to be sufiliciently 

 analyzed by countiug the individuals, and oceanic population statistics 

 were thereby to be made, then this would only be possible 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 

 periods of the year. 



A single "reconnoiteriug voyage" on the ocean, a single "trial 

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

 of the National expedition, can furnish 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 

 arrangement of this numerical protocol, by rational reckoning of their 

 results, a serviceable conce|)tion of the quantity of individuals of the 

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

 computation would give us an approximate coiiception of the conditions 

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

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

 ing upon the whole ocean; for that purpose hundreds of similar com- 

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

 ui)on continuous series of observations during whole years. The zoolog- 

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

 of observations of this character, not such trial trips as the three-months 

 voyage of the National. * 



* In my opinion tlie results of the National expedition of Kiel would bave been 

 quite difterent if it had been carried out in the three months from January to March, 

 inster.d of from July to October. On the whole, the volume of jjlanlvtouic catch, at 

 least in the North Atlantic Ocean, would have more than doubled; in some places it 

 would have been increased many fold. Its constitution would have been entirely 

 different. If the expedition had l)y accident fallen in with a zoocurrent, and its 

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

 certainly been a hundredfold, possibly a thousandffdd, greater. 



