599 



Itu I in April a very rich plankton is met with consisting of Chæto- 

 plankton and Contortoplankton ; tliis plankton difFers Ironi the two 

 previous years, the Chæloplankton of the spring being intermixed 

 with Contortoplankton, whicb before occurred in autumn. This 

 mav appear Strange, hnt in most piaces (the west coasl of Norway; 

 Bohuslån; Denmark) the Contortoplankton attains two maxima, one 

 in the spring and one in the autumn; the spring maximimi did 

 not occnr in the samples of 1897 and 1898. As in 1897, Styli- 

 plankton is met with in Julv, and one of the gatherings (No. 53) 

 contains Phaeocyslis Pouchetii, and the two autumn gatherings (Nos. 

 54 and 55) are very poor, but in the latter there is an indication 

 of Discoplankton. 



1900, Table IV. In March— April 1900 this Discoplankton is 

 well-developed and intermixed with sorae Scotica-forms, which in 

 .lune are replaced by Longipesplankton. In two July gatherings 

 a rich Diatomplankton occurs, which, owing to its great richness 

 in forms, is difficult to cbaracterize; it contains species of Chaeto- 

 ceras (Ch. decipiens, Ch. contortum), Rhizosolenia and lastly Phaeocyslis, 

 and it thus appears to be more particularly a mixture of Chæto- 

 and Styliplankton with Contorto- and Soleniaplankton. In August 

 and September the Peridiniaceae dominate, especially a mixture of 

 Longipes- and Scoticaplanklon. Here then, we have as in 1898, 

 the extreme limit for the cold current. In October the usual Con- 

 tortoplankton occurs, and then we have Disco- and Sphæraplankton. 



1901 , Table V. The 3 gatherings from March show a new 

 neritic association: — S iraplankton characterized by the occur- 

 rence of Thalassiosira g ravida, Nordenskioldii and other forms; Disco- 

 plankton is, moreover, constantly present. — 



On comparing the changes taking place in the associations 

 during these 4 — 5 years, one cannot help noticing how regularly it 

 all happens. A larger or smaller number of neritic associations 

 mav intervene, which depends on accidental circumstances, and the 

 whole series mav be displaced a monlh or more, but the succes- 

 sion of the oceanic associations is the same: — 1. Disco- and 

 Sphæraplankton. — 2. Chætoplankton. — 3. Styli- and Scotica- or 

 Longipesplankton. — 4. Disco- and Sphæraplankton. The alter- 

 nation and succession of the neritic associations will be best under- 

 stood by the following description of the plankton from Nolso- 

 Ijord; as mentioned above the neritic associations may be driven 

 out into the open ocean, but usually at no regular intervals. — 



