OXYGEN CONSUMPTION IN ACIDS. 2Q5 



pipes into the laboratory was found to be toxic. In acidifying 

 the water, concentrated HC1 was regarded as a 10 mol. solution 

 and sufficient of this was added to a measured quantity of sea- 

 water to give theoretically a certain molecular concentration of 

 hydrochloric acid. Actually, of course, owing to the salts in 

 the sea-water, the concentration obtained is less than that given 

 in the tables. The hydrogen ion concentrations of these solutions 

 could not be determined as I did not have with me the necessary 

 outfit. It may be roughly estimated, however, that i/iooo HC1 

 in sea-water is about pH 7.0, 1/800 about pH 6.5, 1/600 about 

 pH 6.0, and 1/400 between 5.0 and 5.5. When allowed to stand, 

 of course, such solutions become continuously more alkaline, 

 owing to the escape of carbon dioxide. For this reason, the 

 solution was not made until a few minutes before it was to be 

 used in the tests. The pH of normal sea-water is about 8.2. 



The acidification of the sea-water has little or no noticeable 

 effect upon the behavior of the animals in the lower concentra- 

 tions, i/iooo mol. or less. In concentrations of 1/800 mol. or 

 greater, the animals are markedly affected. The starfish with- 

 draw their tube feet into the ambulacral groove. The rays are 

 retroflexed towards the aboral surface. In this position the 

 animals remain during the exposure to acid and are apparently 

 unable to move about or to cling with the tube feet. Nudi- 

 branchs display a similar behavior. In the stronger solutions 

 they lose their ability to hold to the substratum with the foot 

 and float about in the water in a state of immobility. The gills 

 however remain expanded and it is not believed that differences 

 in the degree of expansion of these organs are to any extent 

 responsible for the depressing effect of acid on the oxygen 

 consumption. In brief, acidification of the water appears to 

 paralyze the neuro-muscular apparatus and to reduce the animal 

 to a state of forced immobility. Recovery is prompt and com- 

 plete upon return to normal sea-water. None of the concentra- 

 tions used had any injurious effects upon the animals. 



The results of the experiments are given in part in Tables I 

 and II. A typical experiment for each concentration of acid 

 used for one of the starfish species (Patiria miniata) and for the 

 nudibranch is presented in Table I. Three trials of each concen- 



