408 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



figures, that dissolved organic matter is the most import- 

 ant food supply for the majority of aquatic organisms. 



Our own previous work demonstrated to us that the 

 amount of dissolved organic matter in pure sea-water such 

 as is found at Port Erin is so small as to he undetermin- 

 able by any known chemical method, and certainly falls 

 below 1 milligram per litre. 



It is, hence, impossible that in the foregoing experi- 

 ments the animals could have been supported by the 

 organic matter dissolved in the sea-water, for the very 

 utmost available organic matter, even if the organism 

 removed every trace from the sea-water, would have been 

 45 milligrams daily for each of the lobsters, and 90 milli- 

 grams each for the fish and octopus. Now the lobsters 

 used up daily oxygen equivalent to about 160 milligrams 

 of organic matter, and the fish an amount equivalent to 

 450 milligrams, and the octopus to 600 milligrams. 



The Putter hypothesis as to feeding by dissolved 

 organic matter accordingly yields no explanation for the 

 slower falling off in the weights, and as the subsequent 

 experiments show this is due solely to increased water 

 content of the tissues. 



Moreover, the above experiments show the impos- 

 sibility of Putter's position, by exactly similar reasoning 

 to that which he himself uses in proving the inadequacy 

 of the average plankton distribution as a food supply, 

 namely, the inordinate volume of water which would 

 require to be entirely cleared of dissolved organic matter 

 in order to furnish sufficient nutrition. 



If the figure we have stated as the maximum possible 

 for dissolved organic matter in pure sea- water, viz., one 

 milligram per litre, be taken as the basis of calculations, 

 then to keep in equilibrium from this source by complete 

 abstraction of organic matter from the water coming in 



