89' 



■re. diu' miulit in the sufceediiii;' 

 ■^pofics which were mmiorou.s in 



(■(iiiilitions wliii'ii are subject 

 w liicii do take place, occur as 

 It at ieiiLith a point is reached 



(|uantitirs. Such lias at any latc hccn my cxiicriciice. On the 

 otiicr iiMiid 1 have never seen any lai'L.'c iiundicr of rcstiiii;- spores 

 in shallow walci'. 



If tliey survived the suuiuier I 

 year to find (luantities of the same 

 the pi'eeediuL;- one; and consequently a considerable uniformity year 

 after year. But, accordiiii;- to my explanation, one would expect 

 greater variation. 



The oceanic species live und 

 to but little chanw. The chaii-c 

 a rule slowly and ijradually. so t 

 A\hen it is a question of whether or not. 



If, on the other hand, an oceanic species comes into coast 

 water, or into a boundary district between two curi-ents a formation 

 of resting spores might take place, if the species in question had 

 the requisite power. But in such cases, Gran does not consider 

 it to be an oceanic species (but a neritic one). In this way, one, 

 of course, gets as clearly defined a distinction, between oceanic 

 and neritic species, as can be wished for; but such a distinction is 

 at any rate highly artificial and seems to me to be of little use, if 

 Gbax's interpretation of the resting spores is not correct. Besides, 

 I think that the most important question is, whether a given spe- 

 cies can pi'opagate and thrive in the open sea, and this may be the 

 case even if it is possessed of the power of forming resting spores. 

 According to my opinion with regard to them, it might in some 

 cases just be the coast water which is an hindrance, and the oceanic 

 water which is furthering. 



At any rate, it ought first of all to be clearly proved that the 

 resting spores are deposited in large quantities at the bottom of 

 shallow water, and this should not be a very difficult matter. Deep 

 water can scarcely be taken into account, nor yet those spores which 

 have been washed further ■ down than about 50 m.s beneath the 

 surface, to mention a figure which would seem to suit. There must, ! 

 I take it, be great quantities of resting spores present to explain 

 the sudden appearance of large masses of diatoms. 



My experience — as mentioned above — goes to prove that j 

 it is just only in deep water that large quantities of resting spores j 

 are found, and here, as explained above, one must expect to find j 

 them. I have not, however, by direct experiments, become convin- 

 ced that essential quantities of them do not occur at the bottom of 

 siiallow w^ater, and I will, therefore, in this connection, mention 

 that it is quite likely that the usual method of preparing bottom 

 samples gives a negative result, even if they do contain such spoi'es. 



When I above threw out the suggestion, that the hea\4er 

 spores serve to force the individual into deeper water, I do not 

 wish to be understood to mean that their special or only purpose 

 is to make the individual diatom heavier. It is also reasonable to 

 suppose that the formation of resting spores may be a reaction to 

 plasmolysis, caused by salter water. This thought, would, it seems 

 to me, explain certain phenomena of the plankton, although I will 

 not now at present venture to say that this reason is the more 

 decisive. I have not yet sufficiently studied this subject (the for- 

 mation of resting spores). 



As it is always unsatisfactory to attack a given hypothesis 

 — especially one such as this of resting spores which seems to 

 rejoice in numerous adherents — unless another be offered in its 

 stead, I will now mention how I consider the inflow of diatoms 

 occurs. 



If I have undei'stood hydrographers correctly, there is, on the 



surface during the winter months, a tongue of salt watei-, Aviiich 

 flows northwards, fairly parallel to the coast of Norway from the 

 passage between the Fa^'oe Islands and iShetland. This tongue 

 seems to be comparatively nai'row, especially a little to the north 

 01- north east of the passage, and it expands northwards, until at 

 its most northerly end — in the neighboui-hood of Bili-en Eiland — 

 it divides into two or more arms. 



On the right of this tongue of ocean water, there is the coast 

 water oft" the coast of Norway; on its left, there is the arctic water 

 (nearest to the Faeroe Islands it is the East Icelandic Polar Current). 

 This (easterly) tongue of ocean water is displaced and forced in 

 different directions by the water from the arctic regions, now nearer 

 to the coast of Norway, then in the contrai-y direction; and it 

 varies in its distribution northwards (or is mixed in diffoi'ent pro- 

 portions with the arctic water). 



In the spring months, there appears to be a rich diatom plank- 

 ton just in the boundary line between this arctic water and that 

 of the Atlantic. This phenomenon may partly be caused by a 

 purely mechanical crow^diug where the velocity of the current is 

 lowest; but it is also very likely that the .somewhat higher tempe- 

 rature of the mixed water may promote the evolution of the diatoms. 



In Gran's last work (L. 70, p. 158, 160) one learns from the 

 expedition of S/S Heimdal, in May 1901, that there w^as found in 

 the southern section of the „Gulf Stream" (the previously mentioned 

 tongue of ocean water from Faeroe— Shetland northwards) a rich 

 diatom plankton on both sides of the stream, especially on the 

 western towards the Icelandic polar current. Traces of a similar 

 state of things were found in the second section, much more nor- 

 therly, but it was here little noticeable (at that time of year). 



Gean himself mentions that |on the western boundaiy of the- 

 Gulf Stream, a rich neritic plankton consisting of diatoms was found, 

 and this he considers to have been brought hither by the current, 

 probably from the Faeroe Islands. He also mentions that the same 

 state of things has several times previously been noticed at about 

 the same place and time. With regard to the northern section, he 

 hints at an exceedingly long transport of the same neritic forms- 

 northwards to the corresponding boundary line there. 



In this connection, it would be of importance to know whether 

 such an evolution of masses of diatoms takes place in other places 

 on the boundaries between the atlantic and arctic waters, (at a time 

 which is favourable to the development of diatoms, probably ex- 

 cluding the winter months of December, January and February, 

 and perhaps partly also March) or if this production en masse is 

 confined to those places where coast water is present. It is quite 

 likely that the latter is the case, but one can hardly say that it 

 has, as yet, been clearly proved. 



If such mass development should be found in the boundaries 

 as a whole, one of the principal reasons would disappear for con- 

 sidering as neritic such arctic diatoms as have been found repeatedly 

 in large numbers in samples of plankton which have been taken far 

 from the coasts. 



As the tongue of ocean water above mentioned is narrow and 

 varies in its situation and expanse, it is reasonable to conclude 

 that, occasionally during the spring months, the arctic waters wash 

 over it, and become in this way transferred to the coast of Norw^ay, 



To judge from the occurence of the diatom inflow, this would 

 seem to happen regularly at the end of March. (In 1598 parti- 

 cularly early, namely in tlie middle of the month, or perhaps still 

 earliei-. ) 



