390 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



prevent ingress of light, the metabolic exchanges rose 

 again to their former level. 



This growth of vegetation is a factor of error carefully 

 to be guarded against, as the assimilation by green sea- 

 weed is so rapid in good light, that almost all the carbon- 

 dioxide produced by a lobster can be reconverted into 

 oxygen by the vegetation which forms on its own carapace. 



Four large carboys, such as are used for the carriage 

 of vitriol, were used for the experiments. The volume of 

 each carboy lay between forty and fifty litres, and is 

 given accurately in the table of each of the experiments. 

 The animals experimented upon were two lobsters, a fish, 

 and an octopus. 



The sea-water in the two carboys containing the 

 lobsters was changed once daily in the morning, that 

 being found ample to give sufficient oxygen, and also to 

 give good differences, for purposes of titration, in change 

 in content of the water in oxygen and carbon-dioxide. 

 But in the case of the fish and octopus the oxidations are 

 more rapid, and it was accordingly found necessary to 

 change the water twice daily, in the morning, and 

 late at night. Even with this double change of water, 

 so allowing about ninety litres of sea-water daily, it was 

 usually found that four-fifths to five-sixths of the dissolved 

 oxygen had been removed by the respiration of the animal. 

 It is a remarkable and interesting fact that animals so 

 highly organised as a fish and octopus can stand such 

 an oxygen diminution as this (down to as little as 1*5 

 milligram of dissolved oxygen per litre) repeated for some 

 hours twice daily for a period of over thirty days, without 

 apparently causing any injury to the animal. 



The sea-water supply was obtained by a hose pipe 

 from the elevated outdoor tank of the Biological Station. 

 The station supply is pumped daily into this tank from 



