578 JACQUES LOEB 



eggs were then trausferred for from thirty-five to forty minutes 

 to a hypertonic solution (50 cc. sea water + 8 cc. 2^ m NaCl 

 + KCl + CaCl2) a number of them formed membranes and 

 the eggs developed afterward into swimming larvae. 



Recently O. Warburg^ showed that NH4OH diffuses 'rapidly 

 into the sea urchin egg while NaOH does not, and this observa- 

 tion was confirmed and enlarged by Harvey/ This suggested 

 the possibility that, as in the case of acids, weak bases might 

 be found to be more effective in producing artificial partheno- 

 genesis than strong bases. 



1. Method 



In order to obtain comparable results the bases had to be 

 added to a neutral solution instead of to sea water. An m/2 

 solution of (NaCl + CaCl2 + KCl) in the usual proportion 

 was used^ for this purpose. Before the eggs were put into this 

 solution they were freed from sea water by repeated washing 

 in a solution of the same constitution and concentration. From 

 the alkaline solution the eggs were transferred directly into 

 the neutral hypertonic solution. The latter consisted of 50 cc. 

 m/2 (NaCl + CaCls + KCl) + 8 cc. 2^ m of the same mix- 

 ture. From the hypertonic solution the eggs were transferred 

 to normal sea water. They often showed a tendency to stick 

 to the glass. This was overcome by preventing them from 

 settling for about five minutes through gentle agitation. 



2. Comparison of the efficiency of NHiOH and KOH 



To 50 cc. m/2 (NaCl + KCl + CaClo), 0.3 cc. ^ NH4OH, 

 and 0.3 cc. -^ KOH were added respectively. Unfertilized eggs 

 of Arbacia were left in these solutions for six, twelve, twenty- 

 four, forty- two, and sixty-one minutes. Then they were trans- 

 ferred for fifteen minutes into the neutral hypertonic solution, 



' O. Warburg, Zeitsch. f. physiolog. Chem., Bd. 66, p. 305, 1910. 

 ^ Harvey, Jour. Exper. Zool., vol. 10, p. 507, 1911. 



* This proportion is as follows: 100 cc. m/2 NaCl + 2.2 cc. m/2 KCl + 1.5 

 cc. m/2 CaCl.2. 



