GERMAN PLANKTON INVESTIGATIONS. 309 



plankton is evenly distributed in the upper layers of the 

 water. 



The quantitative plankton method has been used in the 

 investigation of both fresh and salt water, and in the 

 latter case both in the open ocean and in the neighbour- 

 hood of the coasts. 



The following salt water areas have been investigated : 



I. — Coastal areas, (a) For several years — Bay of Kiel 



(b) During a whole year — 



In the arctic seas. Karajak-Fiord, in N.W. 



Greenland, 70° N., by Vanhoffen. 

 In the Mediterranean. The Straits of Messina, 



by Lohmann. 

 In the Tropics. The Bay of Ralum, by Dahl. 



(c) In the winter months — 



The Gulf of Naples, by Schiitt. 



II. — Part of the open ocean, by means of a series of 

 investigations carried out during a journey — 



The west and other coasts of the East Baltic (to 



Memel and Gotland). 

 The north part of the North Sea from Skagen 



to the Hebrides. 

 A great part of the Atlantic Ocean during the 



Plankton Expedition (July-Nov., 1889). 

 The area between the Lofoten Islands and the 

 north of Spitzbergen, during the Prince of 

 Monaco's Expedition, in July and August, 

 1898. 

 Numerous investigations of fresh water lakes have also 

 been undertaken, notably one by Apstein on the Lakes of 

 Holstein. 



