1915] OSTERHOUT—PERMEABILITY 245 
circulate freely between them. Care was taken to keep them 
only about two-thirds submerged, so that they had free access to 
air without any risk of drying. 
The tissue had in sea water a resistance of 1020 ohms at 20° C. 
As the temperature of the sea water varied but slightly from this 
during the experiment, all readings were taken at 20° C. On being 
placed in NaCl 0.52M at this temperature, the resistance fell in 
five minutes to 890 ohms; it was then placed in sea water and a 
reading taken ten minutes later showed that it had risen again to 
the normal. The resistance of the apparatus was 240 ohms; hence 
1100 OHMS 
mn Reticn, A ganas 
a) 
5 HOURS 
Fic. 1.—Alterations of permeability shown by curves of the electrical resistance 
of Laminaria saccharina in NaCl 0.52M (unbroken line) and in sea water (dotted 
portion of the curve); the horizontal dotted line (above) shows the resistance of the 
control. 
the net resistance at the start was 1020—240= 780 ohms, and the 
net conductance 1+780=0.00128 mho. The net resistance after 
treatment with NaCl was 890—240= 650 ohms, and the net con- 
ductance 1 +650=0.00154 mho. The increase in permeability, 
therefore, was ©.00154—0.00128= 0.00026 mho, or 20.3 per cent. 
The tissue was then placed in running sea water for 22 hours, 
with the precautions mentioned above. At the end of 22 hours 
the resistance was 1020 ohms at 20° C. An exposure of five minutes 
to NaCl resulted in a drop to 920 ohms, with complete recovery 
within ten minutes. The same treatment was given once each day 
for 15 days. On the tenth day the resistance began to fall off, but 
as this falling off was also shown by the control, which remained in 
