CH. X] THE COXDITIOXS OF LIFE IX THE SEA 211 



the diatoms (which make up the greater part of the catch) we 

 find that the numbers given really underestimate the actual 

 contents of the sea in the region investigated. The area of the 

 mouth of the net was O'l sq. metre, and it was lowered down to 

 20 metres and then hauled up. After correcting for the loss due 

 to the escape of organisms through the pores of the net, and for 

 the filtration loss of the latter, Brandt concludes that the catch 

 must be trebled in order to give the actual contents of the column 

 of water filtered. The amount of dry diatom substance contained 

 in one cubic metre of water was 1'97 grammes, and calculating 

 the amount of proximate food-stuffs contained in this^, we find 

 that one litre of sea water in the Bay of Kiel, on this occasion, 

 contained : 



(1) 0T9 milligramme of proteid, 

 0*05 „ fat, 



0*43 „ carbohydrate. 



Lohmann's figures for the plankton contents of the water of 

 the open sea off Syracuse may be utilised in order to obtain 

 similar values. I have already quoted (in Chapter YIII. p. 166) 

 the description of these catches. The reader will remember that 

 Lohmann made use of various forms of filtering apparatus, and 

 that his figures probably represent the actual contents of the 

 water of the area examined. He found that one cubic metre of 

 the water contained : 



2,082,740 protophyta, 

 325,510 protozoa, 

 17,415 metazoa, 

 and 785,000,000 bacteria. 



Again using Brandt's tables to reduce these figures, we find 

 that the amount of dry organic matter contained in such a catch 

 was 0'01159 mgr. per litre, and further that the quantities of 

 proximate food-stuffs contained in one litre of the water were : 



(2) 0'004 milligramme of proteid, 

 0-0006 „ fat, 



0'004 „ carbohydrate, 



^ Using Brandt's tables in Chem. Zusamm. Plankt. 



14—2 



