18 



købing, so that a column of water of c. 4 fathonis lias been fislied through, 

 but he has every time made 3 hauls with the net. It had beeu better if he 

 had made 4 hauls; the weight of thc plankton caught after the 24tli of April 

 1897, in table IV, could then liave been compared directly to the precediug 

 statements of the weight, now they m\ist be multiplied by ^/... if we want 

 to do so. 



Of coui'se this method of using small bags for quantitative fishery is not 

 quite satisfactory, but it is considerahly cheaper and may very well be adopted 

 for these preliminary investigations. 



The result of these contiuued gatherings at Nykøbing is found in 

 table IV. 



Thero is a striking diminution in the quantity of plankton from October 

 till November. The mean temperature in October was 10,i " G, but in No- 

 vember only 5,3 " C. The saliuit}', on the other hånd, was but little lower in 

 November than in October. 



The whole winter the plankton is very scarce; it does not shoot up again 

 till towards spring-time, the peridinieæ later than the diatomaceæ. Gran says 

 of this: »The Plankton of the Limfjord is, ou the whole, more like that of 

 the Cattegat than like that of the North Sea; it is, however, very different 

 from both. 



From the Cattegat plankton it differs particularly by the alraost complete 

 absence of just the commonest Cattegat forms, viz. : 

 BMsosolenia alata (summer form), 

 Chætoceros constridum (maximum: March — May), 



— curvisefum (liarvest form), 

 Leptocylinårus clanicus (maximum: March— MajO- 



Chætoceros debile I never saw in such huge quantities as from the Lim- 

 fjord; moreover it is here rather a harvest form, while in the Cattegat and 

 Skager Rack it has its maximum in spring. 



In May and June the oceanic forms are predominating in tiie Limfjord 

 (BMsosolenia Shruhsolii , Chætoceros horecde and decipiens), and tlie plankton is 

 quantitatively poorer; the rich neritic plankton of April has disappeared. 



In July a neritic plankton, of mauy species, reappears. From July till 

 October the changes are very gradual, as from February till April. 



It is very interesting to see how the neritic diatomaceæ suceeed one 

 another. They begin in the middle of the winter with Biddulphia anrita (a 

 genuine winter form which is widely distributed) ; then eomes, in February, a 

 new species Lnitderia cystifera. It is very like thc L. confervacea Cl. from 



