OrIGINAL Meruop oF ARTIFICIAL PARTHENOGENESIS 163 
generally, though possibly not always, unable to cause the 
unfertilized eggs of S. purpuratus to develop. into larvae, no 
matter how long the egg is exposed to such a solution. For such 
experiments the alkaline sea-water cannot be used; hence the 
writer chose as a neutral solution a neutral mixture of 100 
ec. NaCl, 2.2¢:c. KCl, 1.5:¢.c. CaCl,,-and 11.6 c.c.-MgCk, 
all the solutions being half grammolecular. 
We call such a van’t Hoff solution neutral when it 
is colored red by neutral red, but turns to orange for a few 
minutes on the addition of only 0.1 e¢.c. of N/100 NaOH, 
afterward becoming red again. The concentration of the 
hydroxylions in such a solution lies below 107° normal, but so 
close to this value that the slightest addition of alkali brings 
up the concentration of the HO ions to this amount; however, 
owing to the diffusion of the CO, of the air into the solution, 
the concentration of the HO ions soon sinks again below the 
limit of 10~® n. 
We shall now illustrate by a few examples the fact that 
even the greatest increase in osmotic pressure will as a rule not 
effect the transformation of eggs of S. purpuratus into larvae in 
neutral solution. To 50c.c. of a neutral van’t Hoff solution, 
8, 12, 16, 24, and 32 c.c. of 23 m KCl solution were added 
respectively. The eggs of one female were divided among these 
solutions after being washed twice in the van’t Hoff solution 
to free them from any trace of sea-water. This precaution 
is essential in such investigations, and has been employed in all 
our experiments. The temperature of the hypertonic solution 
was 13°C. A portion of the eggs was transferred from each 
solution to normal sea-water after 25, 45, 75, 105, 145, 185, and 
220 minutes. Not a single egg developed into a larva. With 
the addition of 32 c.c. of 2 m KCl to 50 c¢.c. of the van’t Hoff 
solution the limit of the permissible osmotic pressure is reached, 
since at higher osmotic pressures the eggs are at once cytolyzed.’ 
lLoeb, Pfliiger’s Archiv, CIII, 257, 1904; Untersuchungen ueber die kinst- 
liche Parthenogenese, pp. 288 ff. 
