NaTuRAL DEATH AND FERTILIZATION 733 
Immature eggs were introduced diréctly into sea-water to 
which 1, 2, 3 and 4c.c. of a .”, HNO, solution had been 
added to each 100 c.c. of sea-water. While, as is usual, a 
large percentage of eggs soon maturated in the normal sea- 
water, maturation did not occur at all in the vast majority or 
in all the eggs contained in the sea-water to which 2 or more 
e.c. acid had been added. The addition of even 1 c.c. of 
acid diminishes the number of eggs that maturate. Butitis 
not even necessary to keep the eggs permanently in neutral 
or acid sea-water in order to inhibit maturation. If 4 or 5 c.c. 
of a *, HNO, solution are added to 100 c.c. sea-water, and 
immature eggs are introduced into such a solution for only 
about fifteen minutes, relatively few eggs maturate when 
they are returned to normal sea-water. Such acidified sea- 
water does not kill the starfish eggs. 
We shall see later that the procedure described here 
which, when used upon immature eggs, prevents maturation, 
brings about artificial parthenogenesis when used on mature 
eggs." 
I have, moreover, been able to convince myself of the 
fact that the eggs which are introduced into acidified sea- 
water in an immature state, can be fertilized by sperm if 
they finally maturate. It is possibly in harmony with what 
has just been said that the addition of NaHCOs, or larger 
amounts of sodium citrate to the sea-water accelerates the 
process of maturation. Free hydroxylions are present in the 
solutions of both substances, and it is possible that their 
addition to the sea-water increases the concentration of the 
free hydroxy] ions in the sea-water. 
But the hydroxyl ions are certainly not the only sub- 
stances in the sea-water which favor or cause the maturation 
of the starfish egg. I soon found that when different speci- 
mens of eggs are taken from the same culture, and the per- 
1 LOEB, FIscHER, AND NEILSON, Pfliigers Archiv, Vol. LXXXVIT (1901), p. 594, 
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