PHYSIOLOGICAL EFFICIENCY OF ISOSMOTIC SOLUTIONS 129 



which is free from oxygen: hence it is possible that there is ji 

 connection between these two facts. 



We now come to the experiments with cane sugar. Accord- 

 ing to freezing-point determinations performed by Dr. W. E. 

 Garrey, the sea-water in Pacific Grove lowers the freezing-point 

 to the same extent as a . 54 m NaCl solution. This agrees 

 pretty well with the above-mentioned data. Since, according 

 to Kohlrausch and Holborn, some 74 per cent of the molecules 

 of NaCl are dissociated at this concentration, a 0.94 m cane- 

 sugar solution is theoretically isosmotic with sea-water. But if 

 experiments are performed on the sea-urchin egg with pure 

 cane-sugar solutions, it will be found that such a solution acts 

 as though it were not isotonic but strongly hypertonic. 0, 1,2, 

 3, 4, 5, 6, 7, and 8 c.c. of 2J m cane-sugar solution were added 

 each to 50 c.c. of 3/4 m sugar solution and the unfertilized eggs 

 of a sea-urchin divided among these after artificial membrane 

 formation. 1 Temperature 12 C. The eggs remained 58 minutes 

 in the solution. The percentage of larvae formed is given in 



Table XV. 



TABLE XV 



Composition of Solution 



Percentage of 



Eggs Developing 



into Larvae 



50 c.c. f m cane sugar +0 c.c. 1\ m cane sugar, 

 50 c.c. f m cane sugar -j-2 c.c. 1\ m cane sugar 

 50 c.c. | m cane sugar +3 c.c. 2^ m cane sugar, 

 50 c.c. f m cane sugar+4 c.c. 2| m cane sugar, 

 50 c.c. | m cane sugar +5 c.c. 2| m cane sugar, 

 50 c.c. f m cane sugar -(-6 c.c. 2^ m cane sugar 

 50 c.c. f m cane sugar -j-7 c.c. 2| m cane sugar, 

 50 c.c. f m cane sugar +8 c.c. 1\ m cane sugar 









 a few larvae 



2 



20 

 60 

 98 

 98 



Hence a mixture of 50 c.c. 3/4 m+6 c.c. 2J m cane-sugar 

 solution acts just as effectively as a mixture of 50 c.c. of sea- 

 water+8 c.c. 2J m NaCl or 50 c.c. \ m NaCl+8 or 10 c.c. 2J m 

 NaCl. A mixture of 50 c.c. of 3/4 m+6 c.c. 2| m cane sugar 



1 The eggs were put into the sugar solution a few minutes after membrane 

 formation. 



