384 DEPTHS OF THE OCEAN chap. 



that this can be consumed by the animals without harm to the 

 plant aggregate. He further assumes that copepods and other 

 multicellular animals require per day a quantity of nutriment 

 equal to a tenth of their own volume, whereas protozoa need 

 half their own volume. In view of what I have previously 

 stated regarding the variations in the rate of production of 

 Ceratiitm, I have no hesitation in declaring that the augmenta- 

 tion of the algae varies within wide limits, and the same is 

 undoubtedly also the case with the nutriment-requirements of 

 the animals. Still I am quite ready to concede that Lohmann's 

 assumptions may apply to the average conditions. The follow- 

 ing table compiled by him, and showing values in cubic milli- 

 metres of plankton per 100 litres of sea- water, will doubtless be 

 of interest : — 



Organic 

 matter in 

 sea-water. 



According to this table the surplus plant substance is not 

 large, and in February there was actually a deficiency. It is 

 possible, too, that Lohmann's assumptions are on the optimistic 

 side, and that he has put the production-capacity of the plants 

 too high, and the nutriment requirements of the animals 

 too low. 



Putter, after studying the quantities of oxygen consumed by 

 different marine animals, both benthonic and pelagic, considers 

 that the augmentation of the plant aggregate by no means 

 suffices as nutriment for the animals. If his view is correct, there 

 must, of course, be other sources of nutriment, both to replace 

 the loss of organic substance which the animals incur by 



