108 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
5. It appeared interesting to determine in what way an 
increase of the concentration of HO ions in the hypertonic solu- 
tion would increase the rapidity of its action. To this end 
not sea-water, but a neutral mixture of m/2 NaCl, KCl, CaCl, 
and MgCl, (in the proportion in which these salts are present 
TABLE X 
Time or EXPOSURE OF THE | 
Eaees To HYPERTONIC 
: PERCENTAGE OF THE Kaas 
Sra-WaTER 
Tuat DEVELOPED INTO 
SwiMMING LARVAE 
Without 
With 
Oxygen Oxygen | 
60 minutes+ 0 minutes 7 
60 minutes+ 14 minutes 4 
60 minutes+ 26 minutes 30 
60 minutes+ 36 minutes 30 
60 minutes+ 46 minutes 90 
60 minutes+ 56 minutes a few 
60 minutes+116 minutes no serve: a the 
ie 
eggs 
in sea-water) was used. To each 50c.c. of this solution, 8 c.c. of 
24 m NaCl solution, also neutral, were added to produce the 
necessary hypertonicity; then, 0, 0.1, 0.2, 0.4, 0.8, and 1.6 
c.c. of N/50 NaOH were added each to 50 c.c. of this mixture. 
The eggs of a S. purpuratus were divided among these solutions 
after membrane formation had been produced by the use of 
butyric acid. Table XI gives the percentage of larvae resulting. 
TABLE XI 
Amount of Alkali Added to the Neutral Hypertonic 
Time of Exposure to the Solution in c.c. of N/50 NaHO 
Hypertonic Solution ; 
0 0.1 0.2 | 0.4 0.8 1.6 
SOMmMINUtES ek ce seie ) a few 5% 5% | afew | afew 
larvae larvae | larvae 
40 minutes..... 5% 10% | 20 20 50% | 20% 
50 minutes...... 20 80 50 80 80 100 
6Oiminutes#ese56.. 25 90 90 90 90 90 
7O:minutes: 2.5..:...- 90 90 90 90 90 
80 
