ARTIFICIAL PARTHENOGENESIS 589 



10. Application of the method to the eggs of other forms 



The method of treating the unfertihzed eggs with NH4OH 

 was also tried on the eggs of Nereis and of Chaetopterus. The 

 eggs of the latter form suffer in the treatment but a small num- 

 ber were caused to segment. The eggs of Nereis, however, 

 could be caused to segment and develop almost normally with 

 this treatment. The method was not varied sufficiently to 

 warrant us in giving details. 



SUMMARY OF RESULTS 



1. The experiments show that the weak base NH4OH is 

 much more efficient for the causation of artificial partheno- 

 genesis in Arbacia than the strong bases KOH, NaOH, and 

 tetraaethylammoniumhydroxide. This fact corresponds with the 

 observation made by the writer several years ago, that the 

 weak acids (like the mono-basic fatty acids or CO2) are much 

 more efficient in the same process than the strong acids. The 

 explanation given by him for the latter case seems to hold for 

 the former, that only that part of the acid or base which is able 

 to diffuse into the egg brings about artificial parthenogenesis. 



2. The unfertilized eggs of Arbacia can be caused to develop 

 into normal larvae by putting them into a mixture of 50 cc. 

 m/2 (NaCl + KCl + CaCls) + 0.3 cc. ^ NH4OH for twenty- 

 five minutes, and afterwards into a neutral hypertonic solu- 

 tion, namely, 50 cc. m/2 (NaCl + KCl + CaCla) + 8 cc. 2\ 

 m (NaCl + KCl + CaCl2) for fifteen minutes (at a tempera- 

 ture of about 22°C.) The eggs must be freed from sea water 

 by repeated washing in a mixture of m/2 (NaCl -f- KCl -\- CaCl2) 

 before the}'' are put into the alkaline solutions. This method 

 is almost as satisfactory as the butyric acid method. 



3. The eggs treated for twenty-five minutes with NH4OH 

 form membranes in the hypertonic solution. They can also 

 form membranes while in the NH4OH solution, but in that 



