162 Artificial Parthenogenesis and Fertilization 



In this case the rise in the rate of oxidations is less than 

 that ordinarily caused by membrane formation with butyric 

 acid in the same eggs. 



TABLE XXXII 



Unfertilized Eggs of S. purpuratus 



2. The hypertonic solutions are much more effective in 

 causing artificial parthenogenesis if some alkali is added. In 

 one experiment 0, 0.5, 1.0, 1.5, and 2.0 c.c. N/lONaOH were 

 added each to 50 c.c. of sea-water-f 10 c.c. 2§ m NaCl solution. 

 The unfertilized eggs of one specimen of S. purpuratus were 

 divided among these solutions and portions of the eggs trans- 

 ferred to normal sea-water after 60, 90, 120, 150, and 240 

 minutes. The temperature of the hypertonic sea-water was 

 13.5° C. Only the two of these solutions with the highest 

 concentration of NaOH (1.5 and 2.0 c.c. N/10 NaOH to 

 50 c.c. of the hypertonic sea-water) caused the eggs to 

 develop into larvae (time of exposure IJ hours). Some of 

 these larvae reached the pluteus stage and swam at the sur- 

 face of the dish. Often, however, the addition of quite a small 

 amount of NaOH was enough to cause development and for 

 the eggs of some females the concentration of HO ions pres- 

 ent in the sea-water is sufiicient. We are dealing here with 

 differences in the eggs of various females. It was found in 

 general that a neutral hypertonic solution was not able to induce 

 artificial parthenogenesis in the eggs of S. purpuratus. Even 

 the maximal permissible increase of the osmotic pressure is 



