FERTILIZATION AND OXIDATION 35 
beyond the four- to eight-cell stage. Addition of 0.1 ¢.c. N/100 
KOH allowed a few eggs to reach the blastula stage; addition 
of 0.2 c.c. N/100 KOH allowed 60 per cent to reach the blastula 
stage and with 0.4 and 0.8 ¢.c. N/100 KOH all the eggs 
developed into larvae. 
If we add more KOH to 50 c.c. of the van’t Hoff solution, 
we find that the addition of 0.4 c.c. N/10 KOH interferes 
already with their development; if we add 0.8 c.c. N/10 KOH, 
or more, to 50 c.c. van’t Hoff solution, no egg can segment.’ 
If one wishes to obtain the best type of larvae it is better 
to add varying concentrations of NaHCO,. If to 50 c.c. of the 
neutral van’t Hoff solution are added 0, 0.1, 0.2, 0.4, 0.8, 1.0, 
2.0 c.c. m/20 solution of NaHCoO,; in the solution without and 
with only 0.1 ¢.c. NaHCO, only early segmentations take place; 
in all the other solutions the eggs will develop into larvae. In 
the solution with 1.0 ¢.c. or more NaHCO, the eggs already 
suffer. 
It seems that the faintly alkaline solution is chiefly necessary 
only for the first development of the eggs of purpuratus. Later 
they are able to develop in a neutral but not in an acid solution. 
The lowest Cuo for the development of the egg of Arbacia at 
Woods Hole is about 10°! N, i.e., these eggs can begin to 
develop not only in a neutral but even in a faintly acid solu- 
tion. This difference between the two kinds of eggs may 
be of some importance in regard to the difference in their 
response to the agencies of artificial parthenogenesis, as we 
shall see later. 
The writer published years ago a paper in which he showed 
that the development of the eggs of Arbacia is retarded and 
finally inhibited if increasing quantities of acid are added to 
the sea-water. He has since vainly attempted to show that 
the rate of development of the sea-urchin egg can be increased 
with the increase of the concentration of hydroxylions in the 
1 Loeb, Biochem. Zeitschr., I1, 88, 1906. 
