EXPERIMENTS ON ARTIFICIAL PARTHENOGENESIS 771 



in such a solution to swimming larvae. Just as hydrogen 

 ions bring about the development of larvae 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 Chaetopterus eggs. These eggs develop when 

 a small but definite amount of any soluble potassium salt 

 (KC1, KNO 3 , K 2 SO 4 ) is added (about 1 to 2 c.c. of a 2^ 

 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 

 Chaetopterus 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 Chaetopterus, 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 



