EXPERIMENTS ON ARTIFICIAL PARTHENOGENESIS 771 
in such a solution to swimming larve. Just as hydrogen 
ions bring about the development of larvee from starfish eggs 
calcium ions bring about the development of Amphitrite 
eggs. The addition of 2 to 5 c.c. of a normal calcium-nitrate 
or calcium-chloride solution to 100 c.c. of sea-water is suffi- 
cient for this purpose. 
I repeated and confirmed this year my earlier experiments 
on the specific effects of potassium ions on the development of 
unfertilized Cheetopterus eggs. These eggs develop when 
a small but definite amount of any soluble potassium salt 
(KCl, KNO,, K,SO,) is added (about 1 to 2 c.c. of a 24 
normal solution of one of these salts to 100 c.c.) to sea-water. 
It is not necessary to remove the eggs from this solution and 
to return them to normal sea-water. It may perhaps be well 
to emphasize especially that calcium and potassium ions have 
no specific effect upon starfish eggs, that potassium ions are 
in the same way unable to cause the development of Amphi- 
trite eggs, and that calcium ions are ineffective in the case of 
Cheetopterus eggs. 
4, The following facts are also indirectly of importance 
for the methods of the experiments on artificial partheno- 
genesis. All the ions which bring about parthenogenesis in 
starfish, Amphitrite, and Cheetopterus, also bring about at the 
same time agglutination of these eggs and the formation of 
giant embryos. The problem at which Driesch once worked, 
and which in sea-urchins is beset with great difficulties, 
namely, to bring about the coalescence of the contents of 
several eggs, succeeds beautifully in these experiments, and 
to a large extent especially in the eggs of starfish. I need 
scarcely emphasize the fact that it is of great theoretical 
importance that the ions which bring about artificial parthen- 
ogenesis also in a definite sense and at the same time alter 
the physical state of the egg. I have not yet succeeded in 
finding a specific ion which brings about the development of 
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