328 С. H. OsTiîNFELD and Ove Paulsen. 



creased greatly in the course of the summer owing to the inflow 

 of fresh water from the melting snow^ of the land, so that on the sur- 

 face it was hrought down to 0-6 — l-8°/oo at the end of July, at the 

 same time that the temperature rose to 3-6°— 45° C, the effect of 

 which was that the marine organisms were for a great part killed, 

 and only the resting-spores of diatoms were living. The samples from 

 this period really contained in the main freshwater organisms, which 

 had been carried out by the freshwater from land, for example, 

 Coelasirum microporiim, Gomphosphaeria lacustris , Anabaena sp., 

 Spirotaenia sp., Staurastrum sp., Hyalotheca sp., and many freshwater 

 diatoms. In August — September the salinity again rose and the 

 temperature sank (ca. 27 — 28°/oo and ca. 0°), and at the same time 

 the freshwater forms disappeared and marine species ruled again. 

 The samples from October 1906 permit us to conclude, that the sali- 

 nity continues to rise, most probably owing to the formation of ice, 

 and the temperature to fall, just as they presumably show the de- 

 mise of the plankton (see above). 



The planton of Danmarks Havn is thus an arctic 

 coast-plankton with a flowering period of short dura- 

 tion in late summer. It is somewhat poor in species and con- 

 sists mainly of neritic diatoms, w^hich have a wide distribution in 

 northern seas, also outside the arctic region. Truly arctic are pro- 

 bably only the following species, none of which were very abundant 

 in the samples: Bacterosira fragilis, Eucampia groenlandica, Chaeto- 

 ceras gracile, Biddulphia arctica, Naviciila septentrionalis, N. Vanhöffenii, 

 Peridinium islandiciim, P. brevipes, P. catenatiim, Gonyaulax iriacantha, 

 Tintinnopsis karajacensis, T. pellucida and Tintinnus vitreus. 



II. Plankton of the drift-ice and coastal waters, 

 a. August 1906. (Table II). 



The samples (11) belonging here were collected during the period 

 from July 31st to August 16th in the ice-filled waters; they fall natur- 

 ally into two groups: 



The outermost group (5 samples) are from water with a temper- 

 ature of —0-7° to —1-9° С and a salinity of 31-2— 32-8'^/oo and they 

 were taken between ca. 6° — ll^'W. L. (ca. 120 — 180 miles from the 

 coast). The plankton is very uniform in all the samples; it consists 

 mainly of diatoms and tintinnids; the most frequent species are 

 Chaetoceras coiwolutum, Rhizosolenia hebetata f. semispina, Rli. obtiisa, 

 Cyttarocylis denticiilata typica and robusta, Peridinium siibinerme, 

 P. curvipes and P. pellucidum. Characteristic, though occurring in 

 smaller quantities, were Coccolithophora pelagica (åend), Pontosphaera 

 borealis, Dinophysis arctica, Peridinium roseum, Dinobryon pellucidum 



