Scientific Proceedings. 



77 



formation of toxic compounds which cause the comparatively rapid 

 disintegration of such eggs. If, however, such eggs are put imme- 

 diately or soon after they have gone through the process of mem- 

 brane formation into hypertonic sea water for from 30 to 60 min- 

 utes, they may all develop at ordinary room temperature and a 

 percentage of these eggs segments perfectly normally and develops 

 into normal embryos. The hypertonic sea water has however this 

 effect only when it contains free oxygen. If we substitute hydro- 

 gen for the air contained in it or if we prevent the oxidation in 

 the egg by adding a trace of KCN to the hypertonic sea water, the 

 eggs will not develop but disintegrate in the way characteristic for 

 eggs with artificially produced membranes that have not been 

 treated with hypertonic sea water. From this I concluded that the 

 hypertonic sea water modifies the process of oxidation in the egg 

 and leads the oxidations into the right channels. There remained, 

 however, an apparent difficulty. In my original experiments on 

 artificial parthenogenesis, not two but apparently only one agency- 

 was employed to cause the developement of larvae from the unfer- 

 tilized egg of the sea urchin, namely, an increase in the osmotic 

 pressure of the sea water. My recent experiments here, however, 

 show that in this purely osmotic method of artificial partheno- 

 genesis, we are in reality dealing with a combination of two differ- 

 ent agencies, one being the increase of the osmotic pressure at a 

 comparatively low concentration of hydroxyl ions, the second the 

 hydroxyl ions at a comparatively high concentration. The proof 

 for this statement rests upon the following experimental facts. 



(a) When the concentration of the HO is below a certain 

 limit, namely, io -6 ^ even the maximal increase of osmotic pressure 

 fails to cause the formation of larvae from the unfertilized eggs. 



(o) When the concentration of hydroxyl ions is high, e. g., 

 \0~ % n a very slight increase of the osmotic pressure is able to call 

 forth the formation of larvae. 



(c) The effects of the two agencies can be separated by first 

 putting the eggs for from 1 j4 to 2 hours into a hypertonic solution 

 with a concentration of hydroxyl ions between icr 7 and io~ 6 ;z and 

 afterwards transferring them for some time to an isotonic solution 

 with a concentration of hydroxyl ions of about 2 or 4 x io~ B n. 

 While no egg that has been exposed to the hypertonic solution 



