KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 57. NIO 7. 57 



and may serve as germs. Even Leptocylindrus itself belongs, I think, to the group just 

 spöken of. Indeecl Gran has observed it passing över to resting spores, but this must 

 be a rare case, since I did not succeed in finding such cells among thousands of Lepto- 

 cylindrus, that I ha ve observed. Only once, I saw it change into what may possibly be 

 considered as microspores (zoospores), in consequence of its having met with a foreign 

 water, too warm and salt for it. But the normal evolution does not seem to lead to any 

 kind of spore-formation. Secondly, it is difficult to see the profit of an intermediate 

 sporal stage, destined to be passed at the bottom, for the cycle of life of pelagic algae, 

 living in such a troubled and restless corner of the sea as the Skager Rak, where very he- 

 terogenous and often exchanged water-masses are superposed. Under these circum- 

 stances, the eventually sinking spores will constantly be exposed to dislocations by the 

 under-currents, whose effects are strongly felt even in relatively isolated fjords, as the 

 Gullmaref jord. Evidently, the major part of the spores will not be able to keep stationary 

 över the resting season, and, as a matter of fact, they disappear completely from our 

 waters soon after being ready, their further fäte being still wholly obscure. 



Of course, such a striking feature of organisation as the formation of »resting» 

 spores must point at a special aim and necessarily be of a great value for the alga under 

 its typical mode of life. It is obvious, that a shrinking, a concentration of the living 

 materia into mostly rounded, relatively small and dense spores will notably increase 

 the power of sinking, by lowering the friction, and thus has the clear purpose of helping 

 a pelagic organism, exhausted for outer or inner reasons with growth and multiplying, 

 into deeper levels, be it in order to rest, be it in order to gain a new kind of water, not 

 »tired out» as the one, from which the cell did emerge. I cannot help thinking, that 

 just to be sa ved from exhausted water-layers, deprived of the necessary aliments by bulky 

 vegetations or of a sufficient amount of gases by a rising of the temperature, is quite a 

 good aim to justify a change into the sporal form, independently of where the spores 

 will arrive the next time. 



If this need of reaching new water-layers be, as I think, the original indu cement 

 to spore-formation, we may further subject the possible fäte of a spore to a closer in- 

 vestigation. Either of the following casualties will happen. 



1. The spore will not meet a water-layer, dense enough to keep it f loating, and thus 

 arrives to the bottom, where it may stay either until vertical currents lift it up again, 

 as is generally the case in lakes, or until horizontal currents carry it away towards 

 perhaps distant regions, as will mostly be the case in f. i. shallow parts of the Skager 

 Rak. In lakes, the spores keep resting for doubtless long times; those of Rhizosolenia 

 longiseta, for instance, the greatest part of a year. In the sea, we cannot state anything 

 of the kind with certainty, since all of the actual periods of rest must not necessarily be 

 spent by ungerminated spores, though here also this will seem most natural to 

 expect from a biological point of view. On the other hand, it is very curious that spores, 

 resting for a considerable space of time in our waters, from which they cannot possibly 

 be completely expelled by currents, as Gran has shown, should ne ver be met with. 

 Thus it is advisable to postpone all hypotheses regarding this problem until more of 

 positive knowledge has been accumulated. But whatever the coming fäte of the spores 



K. Sv. Tet. Akad. Handl. Band 57. X:o 7. 8 



