276 FOUNDERS OF OCEANOGRAPHY 



organic matter arising from one of the reagents used in the 

 analyses. The later experimental work of Henze, of Raben, 

 and of Moore, shows that the organic carbon dissolved in 

 sea-water is an exceedingly minute quantity, well within the 

 limits of experimental error. Moore puts it, at the most, at 

 one-millionth part, or one mgm. in a litre. At the Dundee 

 meeting of the British Association in 1912 a discussion on 

 this subject took place, at which Piitter stiU. adhered to a 

 modified form of his hypothesis of the inadequacy of the 

 plankton and the nutrition of lower marine animals by the 

 direct absorption of dissolved organic matter. Further work 

 at Port Erin since has shown that, while the plankton supply 

 as found generally distributed would prove sufficient for the 

 nutrition of such sedentary animals as Sponges and Ascidians, 

 which require to filter only about fifteen times their own 

 volume of water per hour, it is quite inadequate for active 

 animals, such as Crustaceans and Fishes. These latter are, 

 however, able to seek out and capture their food, and are not 

 dependent on what they may filter or absorb from the sea- 

 water. This result accords well with recorded observations 

 on the irregularity in the distribution of the plankton, and 

 with the variations in the occurrence of the migratory fishes 

 which may be regarded as following and feeding upon the 

 swarms of planktonic organisms. I shall deal with this 

 question of nutrition in marine animals in further detail in 

 the final chapter. 



Our knowledge of the relations between plankton produc- 

 tivity and variation and the physico-chemical environment 

 is still in its infancy, but gives promise of great results in the 

 hands of the bio-chemist and the physical chemist. Recent 

 work by Sorensen, PaHtzsch, Witting, Moore, and others 

 have made clear that the hydrogen-ion concentration as 

 indicated by the relative degree of alkalinity and acidity in 

 the sea-water may undergo local and periodic variations, and 

 that these have an effect upon the living organisms in the 

 water and can be correlated with their presence and abun- 



