MICROSCOPIC MARINE ORGANISMS IN HYDROGRAPHY. 385 



about the close connection between the state of the sea and the move- 

 ments of the air, and the still obscure causes of the migration of fishes 

 may be found to be intimately connected with the change of water 

 containing different kinds of plankton. 



It is thus an important matter that the plankton of the North Sea 

 should be thoroughly and systematically examined ; but for this, inter- 

 national co-operation of all the nations around the North Sea is 

 required. I imagine that a central station, under the direction of 

 competent persons and provided with adequate accommodation, might 

 be erected. Samples could be collected at certain intervals, and by the 

 same kind of apparatus at different stations, and sent to the central one 

 for examination. The details should be published every month, and the 

 general results formulated in a way that would be useful to hydro- 

 graphers, meteorologists, etc. The marine biological stations already in 

 existence will probably be found willing for co-operation in such an 

 undertaking ; but they will be able to collect plankton only near the 

 shores, or at short distances from them. For getting samples from the 

 open seas, the officers of the steamers crossing the North Sea and the 

 Northern Atlantic might be found willing to assist, as the plankton 

 may, as Dr. John Murray hinted to me, be procured by pumping water 

 into a silk net. I recently tried this method whilst crossing from 

 Edinburgh to Guttenburg. I fastened the net to the pump when the 

 deck was being washed, and in this way I obtained sufficient plankton 

 to prove that in the last days of July the North Sea was almost 

 free from diatoms, and its plankton consisted mainly of cilioflagellates 

 and entomostraca. 



