584 JACQUES LOEB 



eggs which are induced to develop under the influence of KOH 

 form a membrane, but that this membrane formation takes 

 place, as a rule, not in the alkaline solution but in the hyper- 

 tonic solution. The egg of Arbacia does not form as distinct 

 a membrane under the influence of alkali as does the egg of 

 Strongylocentrotus. In Arbacia, as a rule, only a fine gelati- 

 nous layer is formed at the surface of the egg through the agen- 

 cies of artificial parthenogenesis. 



When the eggs of Arbacia are put for twenty-five minutes 

 into a mixture of 50 cc. m/2 (NaCl + KCl + CaCls) + 0.3 

 cc. ^ NH4OH and then transferred to a neutral hypertonic 

 solution for about fifteen minutes, (at a temperature of about 

 22°C.), as a rule a large percentage, if not all the eggs, will de- 

 velop into larvae and it will be found that the eggs which develop 

 possess a membrane. The membrane in this case is not formed 

 while the eggs are in the alkaline solution but while they are 

 in the hypertonic solution. When the eggs are left in the alka- 

 line solution much longer than twenty-five minutes membranes 

 may be formed in the latter. 



The following observation is of interest. Eggs were put for 

 forty-five minutes into a mixture of 50 cc. m/2 (NaCl + KCl 

 + CaClz) + 0.3 cc. ^ NH4OH + 5 drops 0.1 per cent KCN. 

 From here they were transferred for fifteen minutes into the 

 neutral hypertonic solution and then into sea water. All these 

 eggs formed membranes but perished by cytolysis, the pigment 

 gathering as a rule in one or more spots of the egg. The reader 

 will remember that such eggs when put directly from the alka- 

 line solution with KCN into sea water (without undergoing 

 a treatment with the neutral hypertonic solution) form no mem- 

 brane, and remain intact, developing normally if later on fer- 

 tilized by sperm. 



Why then does the treatment of such eggs for fifteen min- 

 utes with the hypertonic solution kill them? The experiment 

 seems to indicate that the NH4OH has two effects, one of which 

 consists in inducing the process of membrane formation. This 

 process in this experiment was not inhibited through the pres- 

 ence of KCN in the NH4OH solution. In former papers the 



