Protistplaiikto 



b. Remarks on the Plankton. 



I p. 491. ail evolution of lar^c 



cs |)l;u-c early in the sprintr. 



have called, the inflow of 



the wave of diatoms; Gkan: 



As iiieiitioiuMl ill the iiitroiluctio 

 masses of diatoms in the plankton t 

 Tliis very conspicnous plicnomenoii 

 diatoms. (OsTKXKKi.n: diatomébidi;-e 

 Diatomeen-woliic. ) 



To exphiin ..the large wave of dialdiiis. w hieli every spring 

 rolls over the North Atlantic", Ostknfeld (L. 112, p. 65) suppo- 

 ses tiiat the currents have been in close proximity to the shore, 

 for he considers that the evolution of the diatoms is enhanced, when 

 such is the case; although he does not give his reasons for so 

 thinkiiiL:. As, however, this explanation will not do for all cases, 

 he meiilions that tlie same quickening force, as that of the shore, 

 is found ill the houndary lines ..where different currents glide past 



each othei 



{t1!A> 



in his late.' 



work, has examined into the same pheno- 

 menon, more in detail. On the whole, he appears to agree with 

 OsTEXFELD, at anv rate in so much as that the boundaries of cur- 

 rents and also coast water are necessary for production in large 

 quantities, but he goes a step further and suggests a case for the 

 eftects observed. 



He applies the theory recently advanced by Brandt, and con- 

 siders that the explanation is to be found, either in the fact that 

 in the open sea „there is a constant state of famine, as the supply 

 of nourishment principally comes from the coasts; or else that 

 there is a more active decomposition of nitrogeneous elements in 

 the warmer waters of the Atlantic". 



As to which of these causes is the more decisive, Gran does 

 not give any definite opinion. But he seems most to incline to the 

 famine hypothesis, for, from this starting point, he shows how the 

 boundaries of the different currents must act in the same way as 

 coast lines, by reason of the nourishing matter, which they biing 

 with them, from the rivers of Siberia and the arctic coasts. 



In connection with the foregoing, I will give a brief account 

 of the opinions I have formed after my examination of the coast 

 plankton; I will at the outset meation that 1 have had little or 

 no personal experience of ocean plankton. 



1 also long since came to the conclusion that it is probable 

 that the evolution of the large quantities of diatoms depends upon 

 the mixing of the waters. On the whole, I am of the same opi- 

 nion as Gran, as expressed in the quotation first given from his 

 book. 1 must, however, make exception to the famine hypothesis, 

 which appears to me to give altogether too hopeless a view re- 

 specting pelagic animal life. 



When Gran, however, considers the resting spores (endocysts) 

 left behind in the shallow coast water as the i-cal explanation of 

 the phenomenon, my experience makes it impossible for me to agree 

 with him; in spite of the great attractiveness which at first attaches 

 to this hyiHithesis. As is so often the case, so here, the same 

 conclusions ai'e often arrived at from widely differing hypotheses. 



After Gran's theory the neritic diatoms with resting spores 

 (in contradiction to the oceanic, Avhich have none) leave behind 

 these spores in the coast water after a short period of vegetation. 

 When now the spores sprout, in the following spring they cause 

 the production of the large masses of diatoms. 



What 1 most ob.ie<-t to is, tliat if tliis tjieory Ije correct there 

 would be good reason to concluiie tiiat the .,inflow of diatoms" is 

 a local pheiumienon, at any rate in the fiords. One ought then to 

 be able to conclude tiiat the plankton which flourishes in one tioni 

 would be considerai)ly different from wliat is to be seen in another 

 and distant one. 



It would, moreover, be reasonable that the large evolution would 

 occur in one fiord essentially earlier or later than in ad.jacent ones, 

 according to the different local conditions, which might tend eitiici' 

 to ha.sten or hinder the development of diatoms. 



But evciyoiie who has carefully examined the make-up of the 

 plankton at the time mentioned will have particularly noticed that, 

 taken as a whole, there is a remarkable uniformity in the plankton. 



Of course, thei'e are variations, but these appear to l>e caused 

 more by differences in time than place. 



It .should, however, here be remembered, that the jdankton 

 during „the inflow" is very rich also as to (juality, and contains — 

 especially that of the northern inflow — so many forms difficult to 

 determine (small and with thin walls imperfectly silicated) that it 

 must still be considered too little known. 



In spite of the large number of species, and notwithstanding 

 that there doubtless are sfill many unknown ones, it seems to me 

 that there is such remarkably great uniformity that it is difficult 

 to think of the phenomenon as a local one. 



As mentioned at the commencement, however, there is some 

 ditt'erence between the southern and northern inflow; and this ditte- 

 rence would seem to be constant in the ca.se of a few species. It 

 is highly probable that there is a much greater ditt'erence in the 

 quality than can now be seen; for, as before mentioned, the number 

 is large of those species which it is difficult to determine. If, 

 however, considerations be confined to the predominant species, it 

 will be found that there are some which have hitherto only been 

 found in the noiihern, and not in the southern plankton. For in- 

 stance. Gran long since emphasized the fact that Cha-toceros furcelln- 

 tiis ,,is entirely absent south of »Stadt, and (\ cincfiis takes its place." 



It is also remarkable that the phenomenon occurs simultane- 

 ously at ditterent places. If the inflow is seen in one fiord, it will 

 also as a rule be found everywhere in the district. It is indeed 

 quite difficult to decide whether it has come from the south or the 

 north, that is to say, whether the inflow is at the same time ob- 

 servalile in places to the south, and not in places to the north, or 

 vice versa. 



Here let me call attention to the rapidity with which the in- 

 flow sets in — for thi.s 1 consider to be an especially noteworthy 

 and important circumstance. There is no clearly defined time when 

 the change takes place in the plankton and the inflow is prepared 

 for, but it all happens, so to say, with a bound. 



The species which form the bulk of the inflow are. — as pre- 

 viously stated by Ci-eve and Gkan — for the most part ([uite 

 ditterent ones from those which arc generally found in the plankton, 

 and most of them are arctic forms. This — in addition to several 

 other circumstances — is the reason why Cleve has supposed that 

 there is a current of arctic water along the coast of Norway, right 

 awav down to Skageiak and Kattee-at. 



