191ii] iHlroducliou xix 



iMore time spent in repeating liydrohiologieal observations nnder tlie 

 same controllable conditions, rather than in computing "filtration 

 constants" and improving the accuracy of the apparatus, is the most 

 urgent need. Not only is time wasted in needless refinement of appar- 

 atus, but. as Thorndike (1904. p. 158). says: 



Jluch ignorance is shown liy the many students who ilisparajie all measurements 

 that are subject to a large variable error. They either do not know or forget 

 that the reliability of a measure is due to the number of cases as well as to 

 their variability, and that in the more complex and subtle . . . [phenomena] . . . 

 it is always practicable to increase the number of measurements, but often 

 impossible to make them less subject to variable errors. They also forget that 

 the natural and real variability of the fact itself is often so large as to make 

 the variability due to errors of instruments and observation practically negligible. 



Once this fact is grasped it will be evident that the methods of 

 collecting and exploring employed by most oceanographic expeditions, 

 like the "Challenger." "Blake," "Valdivia." "Siboga. " and even the 

 German plankton expeditions, cannot reveal in any detail the relations 

 maintained between plankton species and their environment. The 

 methods are adequate only for determining the kinds and range of 

 species over extensive areas and for yielding general descriptions of 

 the associated environments. The results embodied in the numerous 

 excellent monographs and reports,' while detailed and comprehensive 

 taxonomically. afford little, if any, reliable evidence concerning the 

 relative abundance of the various species in their horizontal, vertical, 

 or seasonal distribution. The methods are adequate for purposes of 

 scientific reconnaissance, but are not adapted to yielding that detailed 

 hydrobiological information without which the fir.st .step toward under- 

 standing the habits of any marine organism is impossible. It is evident 

 that no institution can obtain this required information iniless its 

 efforts ai'c primarily liiological rather than oeeanographical. 



5. Quantitative ^Iethods Employed at the Scripps Institutions 



There are several marine institutions in Europe that recognize the 

 necessity of quantitative investigations. Among the foremost may be 

 mentioned the Commission for the Scientific Investigation of the 

 German Seas, the International Commission for the Investigation of 

 the Sea, and the Marine Biological Station at Port Erin, Isle of Man. 

 To these we are indebted for much mathematical and experimental 

 knowledge concerned in quantitative estimates of marine organisms, 

 as well as for apparatus for collecting them and for analyzing the 



