772 STUDIES IN GENEKAL PHYSIOLOGY 



the unfertilized eggs of sea-urchins. It would be of interest 

 to determine whether such an ion when it is found also brings 

 about an agglutination of the sea-urchin eggs. 



In other forms, Nereis, Podarke, and Phascolosoma, the 

 experiments have been carried far enough so that we can say 

 that artificial parthenogenesis (swimming larvse) is possible in 

 these. The experiments, however, have not yet been worked 

 out sufficiently in order to allow them to be published. 



We can say with certainty of the methods given here that 

 they lead to successful results in the American forms on the 

 Atlantic ocean. In the attempt to discover new methods it 

 may perhaps be well to keep the following (theoretical) con- 

 siderations in view, which I have discussed in greater detail 

 in various earlier papers. The artificial methods for obtain- 

 ing parthenogenesis must be able, first of all, to favor the 

 liquefaction or other destruction of the nuclear membrane. 

 Secondly, they must also alter in a definite way the physical 

 properties of the protoplasm (viscosity, etc.). It seems that 

 in the eggs in which artificial parthenogenesis has succeeded 

 thus far (and possibly in many, if not all, other eggs) chemical 

 changes take place under natural circumstances in the unfer- 

 tilized egg, which endeavor to alter the egg in the two direc- 

 tions mentioned above; that these, however, under ordinary 

 conditions occur so slowly that the egg dies before it under- 

 goes actual cell-division. Those circumstances which are 

 able to accelerate these natural processes will also bring about 

 the development of the unfertilized egg. 



