Iliird e.rcursion in July 1897, also in the »Sea-eagle«, all three starting from the 

 North Sea off Tlij'boron, and contiuuing tlirough tlie Limfjord; the nurabers 

 at the top of the table (I) refer to the map, page 23. On our first and second 

 excnrsion we went iuto the ('attegat (Nr. 12 — 13), on tlie first even into the 

 Baltic Sea (Nr. 14 betweeu Falsterbo and Stevns). The table further shows 

 how many fathom.s we fi.shed througli (from the bottom to the surface); every- 

 where only vertical haiils were taken with the ordinary Hensen's planktou-bag, 

 with an openiug of 7io D nieter. On the first excursion we used a bag we 

 had borrowed from Hensen, on tlie second and third a bag of the same size, 

 made by ourselves, with one of ApRteins buckets undcrneath, instead of one 

 of Hensen s. We made a comparison, however, betweeu the fisliing-power of 

 the two bags, the result of which showed that it was about the same. The 

 mass of the plankton was determincd, duriug the first excursion, onboard, 

 simply by immersion in water in cc; on the two last excursious, af ter returu- 

 ing home, by weighing it, in gram, the plankton having been kept in weak 

 spirit. The latter method is somewhat more accurate, if only the plankton is 

 dried equally much every time. This is pretty easily done, by filtering it 

 through a circular pieee of silk gauze, which is then moved about on dry 

 filteriug-paper, till it only just leaves a trace of moisture on the paper, in the 

 form of (juite small sejiarate points. The number of cc got by pressing away 

 the plankton turned out to be nearly correspouding to the uumber of grams 

 got by weighing; they are therefore both stated in the tables under the heading 

 of »Gram«. On the other haud it gives a cousiderable difference, whether the 

 fresh plankton is weighed in water or kejjt in spirit in this way, particularly 

 if the spirit is stroug; but also this is, I thiuk, of slight moment with regard 

 to the question with wliich we have here to do. 



On our first excursion the salinity was measured by means of an aero- 

 meter in order to give some orientation also in hydrograpjhic matters. 



As above mentioued Mr. Gran has determined both Peridinieæ and 

 Diatomaceæ. The latter he has divided into oceanic and neritic, and among 

 the neritic he has classed all species in which resting-spores have been found, 

 moreover also some rare species in which we may suppose that resting-spores 

 will be found, and finally 3 common ones: Skeletonema costatnm, Guinardia 

 jhiccida, and Leptoeylindnis dankits. He says, however, that it is not always 

 eas}' to distinguish between neritic and oceanic Diatomaceæ with any cer- 

 tainty. 



It would have been a good thing, if the plankton, all through, could 

 have jioen determined, particularly wilh respect io tho niiinuilti: thi.«, however. 



