FERTILIZATION ON PARTHENOGENESIS. 165 



duction induced by artificial means were also dead, but it is a 

 well known fact that a short exposure to a hypertonic solution 

 results in the production of swimming larvae. Sperm enter the 

 eggs after membrane production but yet do not cause develop- 

 ment. Likewise they enter heated eggs and are also ineffective. 

 Von KnafH ('08) found that heating unfertilized sea urchin 

 eggs to 41 C. led to practically instantaneous cytolysis. But 

 heated to 35 C. for 10 minutes they do not cytolize but remain 

 intact for a considerable length of time. These eggs then are 

 not dead : the very fact that sperm enter them and are found at 

 all levels bespeaks a living condition. These eggs then do not 

 develop because they are dead but because some change has been 

 induced that renders impossible the reaction between egg and 

 sperm. We shall consider this change more thoroughly in 

 Sec. V. 



V. FERTILIZIN AND FERTILIZATION. 

 i. Introduction and Discussion. 



In the preceding section we have caused to be produced 

 certain conditions within the egg that have rendered it incapable 

 of being fertilized, yet in no case can we conclude that the eggs 

 are dead. The initial conditions however we can not doubt 

 have been changed; the egg system has been modified until it 

 is physiologically different from the normal egg. 



Previously the results of analogous conditions have stopped 

 with a morphological description of the condition and a guess 

 at w r hat is happening. The debut of the fertilizin hypothesis 

 however allows us to go a step farther: it allows us not only to 

 postulate certain conditions but also to test for the condition and 

 prove or disprove the hypothesis. 



As pointed out in the introduction the basis of this theory 

 rests upon the presence of a substance s*ecreted by the normal 

 egg. This substance, fertilizin, is considered as playing the 

 active role in fertilization. Activation of this substance is held 

 to be the introduction to and the essential step to the start of 

 the processes or reactions involved in the process. It was 

 further pointed out that this agglutinating principle of the 

 supernatant fluid was not present in experiments in which 



