XII 



THE EFFECT OF THE AGENCIES OF ARTIFICIAL PAR- 

 THENOGENESIS UPON THE OXIDATIONS. THE CY- 

 TOLOGICAL CHANGES IN THE PARTHENOGENETIC 

 EGG ' 



1. The experiments thus far considered have shown that it 

 is possible to imitate the activating effect of the spermatozoon 

 upon the egg of the sea-urchin approximately by submitting 

 the egg to two different processes. The first process consists 

 in calling forth the membrane formation in the egg by a 

 fatty acid (or as we shall see later by a number of other 

 chemicals). This process seems to be the essential feature in 

 the activation of the egg, since it suffices to set in motion the 

 whole apparatus of nuclear and cell division. The second 

 process has only a corrective effect, since the membrane forma- 

 tion alone leads to a rapid disintegration of the egg, unless the 

 temperature is very low. The prevention of this disintegration 

 is brought about by the second process. This second process 

 consists in submitting the egg for a short period to a hypertonic 

 solution containing oxygen (or for a longer period to sea-water 

 free from oxygen). 



We will now consider tlie effects of these two processes upon 

 the oxidations in the egg, and afterward gain an insight into 

 the cytological changes produced in the egg by these agencies. 



We will first consider the effect of the membrane formation. 

 The reader will remember that I had shown that the disinte- 

 gration of the egg which follows the artificial membrane forma- 

 tion at room temperature (if the egg is not treated also with a 

 hj^ertonic solution or lack of oxygen) can be retarded for a 

 long time if the egg is kept without oxygen. From this fact I 



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