XIII 
THE RELATIVE PHYSIOLOGICAL EFFICIENCY OF 
VARIOUS ISOSMOTIC SOLUTIONS: 
As already mentioned, I had in 1900 published the obser- 
vation that the development of the egg of Arbacia can be 
initiated by a pure sugar solution.2 These experiments had 
already shown that the pure sugar solution exerted a stronger 
osmotic effect than it should theoretically. 
The following experiments were performed upon the eggs of 
S. purpuratus in which membrane formation had been previ- 
ously produced by treating them with butyric acid. The 
eggs were placed in the hypertonic solution some ten minutes 
after membrane formation, and hence the time of exposure 
is longer than it would be had they been transferred to the 
hypertonic solution half an hour after membrane formation. 
We will start with experiments with pure sodium chloride 
solution. 
The experiments with pure hypertonic solutions of NaCl 
gave results that are, at first glance, paradoxical; for the eggs 
after membrane formation can tolerate a higher concentration 
of NaCl solution than of hypertonic sea-water. We shall see, 
however, that this paradox finds a simple explanation. The 
unfertilized eggs of a female were made to form membranes by 
treating them with butyric acid, and then (about ten minutes 
later) they were divided among 50 c.c. 4 m NaCl-+3, 4, 5, 6, 
7, 8, 10, 12, 14, and 16 c.c. 2 m NaCl; some of the eggs were 
transferred to normal sea-water after 55, 90, and 120 
minutes. The temperature was 13°C. : 
1 Loeb, ‘‘Ueber den Unterschied zwischen isosmotischen und isotonischen 
Lésungen bei der kiinstlichen Parthenogenese,’’ Biochem. Zeitschr., XI, 144, 1908. 
2Loeb, Am. Jour. Physiol., IV, 178, 1900. 
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