+ oP. T. CLEVE. PLANKTON, COLLECTED BY THE SWEDISH EXPEDITION TO SPITZBERGEN. 
If. Styliplankton (Sign S). The region of desmoplankton, which is subject to 
variation in extent according to the seasons, is surrounded by an irregular band of water 
containing styliplankton. In the west this plankton-type seems always to occur in 
mixture with desmoplankton, and such a mixture characterizes the Caribbean Sea, the 
Antilles-current to the region of Bermuda. About the 40° breadth the styliplankton 
becomes more differentiated and the region increases in breadth towards the European 
and African coasts. It forms a narrow band west of Africa from Cape Verde to Canaries 
and occupies the triangular space between the Azores, the English Channel and Bermuda. 
The extent of the region is subject to great variation according to the seasons. In the 
summer it approaches towards the Farée Channel (probably also towards Iceland) in a 
mighty tongue, which sends branches through the English Channel into the German Ocean 
and around Scotland into the North Sea. When the water enters the North Sea its salinity 
becomes lowered by admixture of the continental coast-water and, consequently, the 
plankton becomes also modified. Some of the species die away, others multiply, and 
thus are originated in the North Sea two important derived styli-planktontypes, the 
tripos-plankton in the north and the didymus-plankton in the south. I have distinguished 
as a third type of North Sea plankton the halosphera-plankton. This kind also originates 
from the styliplankton by an considerable increase of the green alga Halosphera viridis, 
which seems to take place in the autumn around Farée, from whence it descends to Scot- 
land and enters the North Sea finally reaching Skagerack. 
The styliplankton-water, which in the beginning of the summer reaches the Farde 
Channel proceeds during the autumn towards Spitzbergen. 
The temperature of this water varies usually between 10° and 20° and the salinity 
is about 35 p. m. 
The number of organisms constituting the styliplankton is very considerable and 
the flora and fauna are subject to a great variability according to the breadth and the 
season. Some species appear simultaneously at the African and South American coasts, 
others occur in the whole region, others again scem to be limited to the eastern part. 
I name among the more common and characteristic forms the following, marking with 
e such forms, as occur in the eastern Atlantic. With s I denote forms, which as a 
rule do not pass over the Farde Channel, and with n forms which enter the northern 
Atlantic. 
Animals. Plants. 
Acartia Clausii (e n), Halosphera viridis (n), 
Centropages typicus (n), Ceratium (trip. v.) auritum (e 8), 
Clausocalanus arcuicornis (s), C. candelabrum (s), 
Coryceus rostratus (e s), C. furca (e n), 
Mecynocera Clausi (in the spring s), C. lineatum (n), 
Microsetella atlantica (n), C. reticulatum (s), 
Oithona plumifera (s, n rarely), Dinophysis homunculus (s), 
O. similis (n), Diplopsalis lenticula (n), 
Oncea minuta (e n), Gonyaulax, polygramma (n), 
Paracalanus parvus (n), Peridinium divergens (n), 
