STUDIES IN ARTIFICIAL PARTHENOGENESIS. 185 



a direct consequence of the textbook definition of potential at a 

 point, as the amount of work done by the electric field on unit 

 charge, when it is brought to that point from infinity. 



Moreover, even if we could accept some of the extiemely 

 dubious evidence that has been offered in favor of increased 

 permeability, no one has ever tried to show that all parthenogene- 

 tic agents do cause increased permeability. In fact R. Lillie 

 has at times assumed that hypertonic sea-water and that mag- 

 nesium salts cause a decrease rather than an increase in per- 

 meability, and yet hypertonic sea- water, even in the presence of 

 magnesium salts, produces initiation of development. 



Of Loeb's ideas concerning the initiation of development only 

 a bare outline is possible here. Recently, he is "inclined to be- 

 lieve that in all cases in which an unfertilized egg has been caused 

 to develop a typical or atypical membrane had been formed." 1 

 This membrane "formation," which, as we have seen, Loeb 

 regards as a swelling process, is the important initiative factor. 

 It causes directly an increase of oxidations, but leaves the egg in 

 a sickly condition, hence it is necessary to provide a corrective 

 agent which may be either oxygen-containing hypertonic sea- 

 water or the absence of oxygen. The theory of the necessity 

 of the corrective factor need not concern us here, for we are 

 primarily interested, not in the best method of obtaining arti- 

 ficial parthenogenesis, but rather in the nature of the physical 

 or chemical change which causes any initiation of development. 

 Loeb believes this change to be an increase in oxidations. In 

 support of this view he has accumulated a mass of data. He 

 first showed that in his original method of using a hypertonic 

 solution alone, artificial parthenogenesis could only be produced 

 in the presence of oxygen. More recently he has measured egg 

 oxidations and has confirmed Warburg's observation that mem- 

 brane "formation" produces a great increase in oxidations. 



According to Loeb's measurements, any cytolytic change re- 

 sults in a great increase of egg oxidations. 



B. The Action of Hypertonic Sea-water in the Presence of KCN. 



Loeb was originally led to adopt the oxidation theory, by 

 the fact that either the addition of KCN, or the removal of oxy- 

 1 Loeb, '130, p. 223. 



