6 vv. T. CLEVE. PLANKTON, COLLECTED BY THE SWEDISH EXPEDITION TO SPITZBERGEN. 
The temperature varies usually between about 5° in the winter and 14° in the sum- 
mer, and the salinity is about 34 p. m., but these figures are subject to great variations 
according to relative abundance of oceanic or coast-water that enters in the composition 
of the triposplankton-water. 
The triposplankton is chiefly constituted by cilioflagellates and entomostraca, the 
diatoms being almost absent. As stated above the animals are to a great extent of the 
same species as in the didymusplankton, which is easily explained as both types are 
derived from styliplankton. 
Among the organisms we note the following: 
Animals. Plants. 
(Sagitta bipunctata), Ceratium furca, 
(Acartia Clausit), . C. fusus, 
Anomalocera Patersonii, C. tripos, 
Calanus finmarchicus, C. trip. v. macroceros, 
(Centropages typicus), Peridinium divergens. 
(Oithona similis), 
(Paracalanus parvus), 
Pseudocalanus elongatus, 
Temora longicornis, 
Evadne Nordmannii, 
E. spinifera, 
Podon intermedius. 
Many of the species of the styliplankton also enter into the triposplankton, as 
Acanthometron quadrifolium. Plectophora arachnoides, probably originally belonging to 
the chetoplankton and abundant around Scotland, enters also frequently into the tripos- 
plankton. 
I. Chetoplankton (Sign C). This planktontype occurs in the western ‘and 
northern parts of the Atlantic only and during the spring. From March to June or July 
it can be traced from about the 40° Lat. and 70° Leng. to the Newfoundland Banks and 
to the south of Iceland, from whence it turns across the Fardée Channel and enters the 
North Sea, replacing its triposplankton, and reaches the coasts of Scandinavia. It dis- 
appears in the summer, becoming replaced by styliplankton, but rules in July and August 
around Spitzbergen. When the water with the chwtoplankton touches the coasts, especially 
of Iceland, it sweeps away the neritic plankton there and spreads it along the coasts of Scot- 
land and Scandinavia, where it enters into the fjords. Thus many species of northern origin 
may remain during the summer cmprisoned in the fjords, especially in their deeper water. 
The temperature of the chatoplankton-water varies usually between 5° and 9° and 
the sulinity is about 35 p. m. 
The organisms of the chetoplankton are chiefly diatoms, especially Chetoceros deci- 
piens and Ch. constrictus. C. borealis and C. criophilus occur both in cheeto- and tricho- 
plankton so that it is difficult to decide whether they belong to one or the other type. 
