Physiological Efficiency op Isosmotic 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 . 54 m NaCI 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 2| m cane-sugar solution were added 

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



Composition o( Solution 



50 c.c. f m cane sugar+0 c.c. 2j m cane sugar. 

 50 c.c. J m cane sugar-|-2 c.c. 2i m cane sugar. 

 50 CO. i m cane sugar+S c.c, 2J m cane sugar. 

 50 c.c. f m cane sugar-|-4 c.c. 2| m cane sugar. 

 50 c.c. I m cane sugar-|-5 c.c. 2J m cane sugar. 

 50 c.c. f m cane sugar-f-6 c.c. 2 J m cane sugar. 

 50 c.c. f m cane sugar-(-7 c.c. 2i m cane sugar. 

 50 c.c. f m cane sugar+S c.c. 2^ m cane sugar. 



Percentage of 



Eg^s Developing 



into Larvae 









 a few larvae 



2 

 20 

 60 

 98 

 98 



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

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

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



