282 University of California Publications in Zoology [Vol. IS 



of the plankton concept must be false. Any given plankton species 

 must either control its own distribution to a significant extent or it 

 must tend to be distributed in accordance with the uniformity 

 postulate, i.e., like the salts of the sea. 



That this postulate actually does lie at the foundation of a large 

 amount of quantitative plankton research is evident from the extent 

 to which what might be called "rain gauge" methods of collecting 

 are employed. Sweeping statements are not infrequently made rela- 

 tive to the distribution of plankton organisms over large areas of the 

 sea which are based upon the assumption, more or less unrecognized 

 perhaps, that OMdng to passivity and consequently to uniformity, one 

 or at most a very few hauls, carefully made with a net whose "filter- 

 ing capacitj^" is accurately determined, justifies the generalizations 

 (Michael, 1916, pp. xvi-xix). Maps and charts are continually being 

 published showing the distribution of various so-called types of plank- 

 ton throughout large portions of the globe, the reliability of which, 

 with few exceptions, rests upon rain gauge methods of collecting, 

 which methods in turn, of course, depend upon the validity of the 

 concept of passivity and uniformity. 



Nothing is more natural, perhaps, than to fall into the error of 

 supposing that, because the locomotive powers of many plankton 

 organisms are too feeble to permit headway against a current, there- 

 fore locomotion has a negligible effect on the distribution of such 

 organisms. In thus overlooking the fact that the ocean, being a 

 body of three instead of two dimensions, may permit plankton organ- 

 isms with feeble powers of locomotion to control their horizontal dis- 

 tribution by means of vertical movements, it is not surprising to find 

 that such organisms are generally regarded, so far as concerns their 

 horizontal distribution, as physical particles which are carried hither 

 and thither by wave, tide, and current. In spite of the noteworthy 

 investigations of the Port Erin Marine Biological Station, Isle of 

 Man, as well as those of various individuals, which have established 

 facts wholly inconsistent with this conception, it not only persists but 

 is made apparent in almost every standard text or reference book 

 dealing in any way with plankton organisms. 



"Witness, for example, the following opening statement quoted 

 from Steur's Flanktonhunde (1910, p. 1) : "Die Planktonkunde oder 

 Planktologie befasst sich mit der Erforschung jener im freien "Wasser 

 schwebenden* grossenteils mikroscopischen Lebenwesen, die wir heute 



* Italics in this and two following paragraphs inserted by author. 



