ARTIFICIAL PARTHENOGENESIS AND OXIDATIONS 123 



of the egg to its normal limit might fit those cases in which 

 the hypertonic treatment follows the artificial membrane forma- 

 tion, but it is difficult to understand how it can be made to 

 harmonize with the fact that the treatment of the egg with a 

 hypertonic solution is equally efficient if it precedes the artificial 

 membrane formation by twenty-four hours or more. More- 

 over, we shall see later on that bases act somewhat like acids 

 in inducing membrane formation, and that the eggs must also 

 be exposed to the hypertonic solution. In this case both 

 agencies, the base and the hypertonic solution, may be combined 

 to act simultaneously upon the egg with good results. This 

 fact seems also unintelligible on the assumption that the bases 

 increase the permeability of the egg (to allow some of its con- 

 tents to escape), while the hypertonic solution has the opposite 

 effect. And finally one does not understand that a hypertonic 

 solution of NaCl (e.g., 50 c.c. m/2 NaCl -f 12 or 16 c.c. 2 m 

 NaCl), which acts as a corrective agent upon the eggs after 

 membrane formation, should diminish their permeability, since 

 all our experience indicates that such a solution injures the sur- 

 face of the egg and increases its permeability. 



II 



8. We will now briefly mention some cytological points 

 worthy of discussion. E. Hindle has investigated the cytologi- 

 cal changes in the eggs of S. purpuratus which had been treated 

 with butyric acid and subsequently with a hypertonic solution. 

 He found that the changes taking place in such eggs were almost 

 identical with those which take place after the entrance of a 

 spermatozoon. Hindle 1 gives the following description: 



The interval (about 20 minutes) between the transference of the 

 eggs from butyric acid to normal sea-water and their subsequent 

 treatment with hypertonic salt solution is characterized by the altera- 

 tions in the appearance of the cytoplasm and nucleolus, and the 



1 E. Hindle, Archiv /. Entwicklungsmechanik, XXXI, 145, 1911. 



