Shelf ord. — Physiological Characters and Depth 195 



quicker than those from the lesser depth. Orabs show 

 similar relations. The data suggest that those that live 

 in the dark are more sensitive than those from the light, 

 which accords with the results with crabs from differ- 

 ent depths. 



III. — RESISTANCE TO FRESH WATER. 



Marine animals do not generally survive for any 

 length of time in fresh water or in water without their 

 normal salt content. Taking for example one of the 

 shrimps noted in the preceding table we find that loss 

 of equilibrium follows in a few minutes after the animals 

 are immersed in the fresh water. 



Table II. 



Showing the Survival of Marine Shrimps from different 

 depths in Fresh Water. 



Here again as in the case of temperature the shrimps 

 from the shallower water survive longest. The same 

 general results were obtained with mussels, barnacles, 

 etc. 



IV. — RESISTANCE TO ALKALINE AND ACID WATER. 



The experiments with herring showed that the fishes 

 are much influenced by the reaction of the water, i. e., 

 whether it is acid or alkaline. Accordingly a series of 

 experiments was run to determine the relative resistance 

 of the animals from different depths to acidity and 

 alkalinity. 



