M. H. JACOBS. 



TABLE I. 



EFFECT OF APPLYING CENTRIFUGAL FORCE OF 150 TIMES GRAVITY AFTER VARIOUS 



EXPOSURES TO CARBON DIOXIDE. 



Time of Exposure. Paramcecium. Colpidium. 



i minute Slight evidences of liquefaction. Slight evidences of lique- 

 faction. 



5 minutes Liquefaction more distinct ; body Liquefaction more dis- 



somewhat shrunken. tinct. 



10 minutes Practically all individuals show Liquefaction very clear. 



complete separation of food 

 vacuoles. 



15 minutes About the same; body beginning Separation of food vac 



to swell. uoles almost complete. 



20 minutes Same; body more swollen. Same; body somewhat 



swollen. 



25 minutes A few show failure of food Same as 20 minutes. 



vacuoles to separate. 



30 min'utes Same as 25 minutes. Same as 20 minutes. 



35 minutes Same as 25 minutes. A few show incomplete 



separation. 



40 minutes Many show no separation. Less complete separation. 



50 minutes Most individuals show no sep- More show absence of 



aration. separation. 



50 minutes Absence of separation in prac- Separation absent in most 



tically all ; recovery almost individuals ; recovery 

 100 per cent. almost 100 per cent. 



56 minutes Same as 50 minutes; recovery Same. 



about 75 per cent. 



65 minutes Same; recovery about 25 per Same. 



cent. 

 75 minutes All dead. Same; many recoveries. 



It is easy to demonstrate that carbon dioxide influences pro- 

 foundly the consistency of the protoplasm of Arbacia eggs. In 

 numerous experiments a five-minute exposure to sea water practi- 

 cally saturated with this gas was found to prevent stratification 

 almost completely when the eggs were centrifuged for two minutes 

 with a force estimated at 1,600 times that of gravity, while the 

 controls in normal sea water showed the typical separation de- 

 scribed by Lyon. That this result is due not to the hydrogen-ion 

 concentration of the external medium as such, but rather to its 

 carbon dioxide content (the carbonic acid probably penetrating the 

 egg in an undissociated form or as CO 2 and subsequently dissoci- 

 ating within the cell), is shown by a comparison of the effects of 



