248 L. V. HEILBRUNN. 



If this view is correct then the fact that mercuric chloride 

 solutions are effective in causing membrane elevation can not 

 be used as an argument against the surface tension theory. If 

 the sublimate forms chlorine we know that a substance of 

 extremely low surface tension must be present. 



It is possible that many more facts with regard to the action 

 of mercuric chloride on egg cells or cells in general might easily 

 be obtained by a further study of the sea-urchin egg in the 

 presence of this reagent. Our only interest in the subject lay 

 in the possibility of overthrowing the surface tension theory of 

 membrane elevation. As soon as it was evident that no such 

 overthrow was possible on the basis of the mercury evidence, no 

 additional experiments were planned. 



SUMMARY. 



1. Dilute solutions of mercuric chloride in sea-water cause 

 typical membrane elevation in the sea-urchin egg in spite of the 

 fact that they presumably do not lower surface tension. 



2. The action of the mercuric chloride is favored by aging the 

 eggs. Eggs fresh from the ovary are not acted upon, and the 

 percentage of membrane elevation on treatment with the subli- 

 mate solution increases in proportion to the time the eggs have 

 stood in sea-water before being subjected to the reagent. 



3. The favorable effect of aging is apparently due to the 

 removal of carbon dioxide. The addition of carbon dioxide 

 prevents membrane elevation by mercuric chloride. 



4. If eggs are centrifuged one or two minutes after the treat- 

 ment with mercuric chloride is begun, membrane elevation is 

 generally prevented. 



5. Solutions of mercuric chloride in contact with eggs lose 

 their power of provoking membrane elevation. 



6. The facts cited in 4 and 5 are regarded as evidence in favor 

 of the view that mercuric chloride reacts with the jelly or cortex 

 of the egg to form chlorine. Such a reaction is in accord with 

 the usual behavior of mercuric chloride in the presence of organic 

 materials. 



7. Chlorine gas is effective in producing membrane elevation. 



8. The action of mercuric chloride in causing membrane eleva- 



