204 JACQUES LOEB 



The description of an experiment will illustrate this point. 

 The unfertilized eggs of one female S. purpuratus were put for 

 ^, 1, 1|, 2, 2^, and 3| hours into hypertonic sea water (50 cc. 

 sea water + 9 cc. 2.5 m NaCl + KCl + CaCls). None of these 

 eggs developed into larvae and none of the eggs that had been 

 up to 1| hours in the hypertonic solution segmented. Of the 

 eggs that had been 2 hours in the hypertonic solution 0.5 per 

 cent went into the two-cell stage but did not develop beyond this ; 

 of the eggs that had been 2| and 3j hours in the hypertonic so- 

 lution 10 per cent segmented into the two- or as far as the four-* 

 cell stage. Practically all the eggs were intact the next day. 



Twenty-two hours later part of each lot of these eggs was 

 treated 1| or 3 minutes with propionic acid (2.8 cc. i^ acid to 

 50 cc. sea water) to induce membrane formation. All formed 

 tight fitting membranes. The result was as follows. The eggs 

 that had been treated with the hypertonic solution ^ and 1| 

 hours disintegrated after the artificial membrane formation. 

 The exposure to the hypertonic solution had been too short to 

 produce a corrective effect. Among those treated for 1| hours one 

 swimming larva was found the next day. Of those that had been 

 in the hypertonic solution for 2 hours, 25 per cent segmented 

 normall}^ after the artificial membrane formation and developed 

 into perfect blastulae; of those treated with hypertonic solution 

 for 2^ and 3j hours practically all developed but many of the 

 blastulae were sickly, a sign that the eggs had been a little too 

 long in the hypertonic solution. 



Forty-eight hours after the treatment with hypertonic solu- 

 tion a second portion of the eggs that had been exposed 2| hours 

 to the hypertonic solution was caused to form membranes by 

 the treatment with propionic acid. The eggs had a tendency to 

 stick to the glass but all segmented regularly and developed into 

 blastulae which appeared normal. 



Three days after the treatment of the eggs with the hypertonic 

 solution another lot (those that had been two hours in the hyper- 

 tonic solution) was treated with propionic acid. Those eggs that 

 were still alive formed tight fitting membranes and all began to 

 segment regularly. A few developed into normal blastulae. 



