624 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



isms ill siiitile icgioiis (»f ciirreiits, and lias twisted it in favor of his 

 theory of the regular distrihution of the planJiton: 



The tests of tho volunio of tbe plankton show that, live times in the north, once 

 north of Ascension, extraordinarily Innjf tatches ( !) were made. Tlioso must liave been 

 cansed by various cifne»(<8 in this region, and can therefore be left out of consider- 

 ation (9, p. 249). 



It seems to me that Henseu would have done better to take into 

 consideration these and other facts observed by him rehttive to the 

 iineiiual phinkton distribution before he built up his fundamental, 

 certainly adequate, theory of the equality of the same. This was to be 

 expected, since he himself in his first oceanic plankton studies (1887) 

 observed mauy ''rem a rlxahle inequalities,^^ ^u(\. his own tables furnish 

 proof of this. While he many times mentions the immense swarms of 

 Medusoi and declares this " quite superabundant accumulation to be 

 mysterious," he adds: "such places must be avoided in this fishery" (9, 

 pp. 27, 65). When Ilensen later, in comi)arino; the difl'ereiit catches of 

 copepods (one of the most important jilanktonic constituents), finds 

 that the distribution of the plankton in the ocean is very irregular 

 and that the constitution of this seems to very strongly contradict 

 his general conceptions of natural life (0, p. 52), he holds it to be best 

 that these catches, which are of "such a different kind, should be 

 excluded from consideration" (pp. 51, 53). Also, in the case of Sagitta, 

 which Ilenscn reckons with the copepods as belonging to the uniform 

 perennial plankton, he finds "throughout not the equality which one 

 might expect, but much more remarkable variations" (p. 59). 



These "surprising inequalities," "variations even to tenfold," he finds 

 in case of the Daphnidw (pp. 54, 5G) and Hyperidw (p. 57), the pelagic 

 larvaj of snails and mussels (pp. 57, 58), Appendicularia and Salpa 

 (pi). 63, 64), the Medusce and Ctenophorea (64, 65), the Tiutinnoids (p. 

 68), the Feridiniw (j). 71), and even in the Diatoms (]). 82) — in brief, 

 in all groups of pelagic organisms which by the numerous production 

 of individuals are of importance for the plankton and upon which 

 Ilensen employs his painstaking method of calculation by quantitative 

 planktonic analysis. If one freely "sets apart from consideration" 

 all these cases of remarkable inequality (because they do not fall in 

 with the theoretically preconceived ideas of the equality of planktonic 

 composition), then finally the latter must be proved by counting. 



BatJiycurrents or deep streams. — Through recent investigations, par- 

 ticularly of Englishmen (Carpenter, Wyville Thompson, John Murray, 

 et a7.), we have become acquainted with the great importance of the 

 submarine currents or deep streams. It has been demonstrated that 

 the epicurrents, or the surface streams, furnish us no evidence rela- 

 tive to the understreams to be found below them, whicli we name bathy- 

 currents. These undercurrents may in diflferent dcipths of the ocean 

 have a (luite diti'erent constitution, direction, and force from the over- 

 currents. This is as true of the great oceanic as of .the local coast cur- 

 rents. If the more accurate study of marine currents is a very difficult 



