Some Experiments on the Resistance of Sea-urchin Eggs 

 to Sulphurous Acid 



Ada R. Hall 



University of Oregon, Eugene 



Recently a method for the treatment of the sewage of cities having 

 over 50,000 inhabitants has been suggested whereby, thru treating with 

 sulphuric or sulphurous acid (Miles Acid Process), several valuable sub- 

 stances will be recovered, and the effluent which goes into the rivers 

 or bays will be essentially free from dangerous bacteria. This will 

 prevent typhoid infection of oyster beds ; but there arises a question 

 as to whether the acid which goes into the water will injure oysters 

 and other valuable animals. Considerable work along this line has been 

 done with adult forms by Dr. V. E. Shelford. This paper presents a 

 rather brief study of the effects of sulphurous acid on eggs and larval 

 stages. The work was done in the summer of 1918 at the Puget Sound 

 Biological Station at Friday Harbor, Washington. 



The material used in most of these experiments is the large purple 

 sea-urchin, Strongylocentrotus franciscanus Ag. This occurs abundantly 

 along clean rocky shores at depths from 6 to 18 meters. This is a par- 

 ticularly good species for embryological work, as the eggs are large 

 and fairly clear and the different cleavage stages can be easily followed. 

 Another advantage is the very large number of eggs furnished by one 

 individual. These can be obtained unfertilized, so that the earliest stages 

 are always to be had for experimental work. The adults were exposed 

 to the same condition as the eggs for comparison of their resistances. 

 Experiments were also tried on medusae (Phialidium gregarium Haeckel 

 and Thaumantias cellularia Haeckel), as index organisms. 



A little preliminary work was done on gastropod mollusk eggs which 

 occur in great abundance on Zostera (eel-grass) and Ulva. These, how- 

 ever, are encased in jelly, which with the egg membrane, prevents the 

 entrance of the acid when solutions weaker than N/300 of acid were used. 

 In the Miles Acid Process solutions of this strength would never be 

 reached. A naked egg was therefore chosen for the work. 



On account of the instability of sulphurous acid, solutions of this 

 had to be renewed frequently. Furthermore the exact reactions of sul- 

 phurous acid in sea-water are not known. Whether it merely dissolves 

 and by its own dissociation gives a certain hydrogen ion concentration or 



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