PHYSIOLOGICAL EFFICIENCY OF IsosmMoTIC SOLUTIONS 129 
which is free from oxygen: hence it is possible that there is a 
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 0.54 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 25 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.! Temperature 12°C. The eggs remained 58 minutes 
in the solution. The percentage of larvae formed is given in 
Table XV. 
TABLE XV 
Percentage of 
Composition of Solution Eggs Developing 
into Larvae 
50 c.c. 2 m cane sugar+0 c.c. 2 m cane sugar......... 0 
50 c.c. 2 m cane sugar+2 c.c. 2} m cane sugar.........| 0 
50 c.c. $m cane sugar+3 c.c. 2} m cane sugar.........| a few larvae 
50 c.c. 2 m cane sugar+4 c.c. 2} m cane sugar......... 2 
50 c.c. 2 m cane sugar+5 c.c. 2} mM cane sugar......... | 20 
50 c.c. 2 m cane sugar+6 c.c. 23 m cane sugar......... 60 
50 c.c. 2 m cane sugar+7 c.c. 2} m cane sugar......... 98 
50 c.c. 2 m cane sugar+8 c.c. 2} m cane sugar......... 98 
Hence a mixture of 50 c.c. 3/4 m+6 c.c. 23 m cane-sugar 
solution acts just as effectively as a mixture of 50 c.c. of sea- 
water+8 c.c. 24 m NaCl or 50 c.c. } m NaCl+8 or 10 c.c. 23 m 
‘NaCl. A mixture of 50 c.c. of 3/4 m+6 c.c. 23 m cane sugar 
1 The eggs were put into the sugar solution a few minutes after membrane 
formation. 
