142 PROBLEMS OF FERTILIZATION 



time in water, was was added freshly prepared milt as 

 follows : 



Percentage of 



Milt Added Fertilized Eggs, 



after i.e., Segmented 



Lot i 2 min. 40 



Lot 2 4 min. 17 



Lot 3 6 min. 10 



Lot 4 8 min. 5 



Lot 5 10 min. o" 



Even two minutes in water has great detrimental effect, 

 and at ten minutes all eggs have lost capacity for ferti- 

 lization. Similarly the egg of the frog is incapable of 

 being fertilized after lying in water a short time (Spal- 

 lanzani and others). 



We can explain such cases, as already suggested, 

 by the loss of the hypothetical fertilizin. Other eggs 

 are apparently better protected with reference to their 

 fertilizin content. Starfish eggs rapidly lose capacity 

 for fertilization after separation of the first polar body. 

 The egg of the sea urchin will bear repeated washings 

 in sea-water without loss of fertilization capacity; but 

 after a certain number of washings before insemination 

 the developmental energy of the fertilized eggs becomes 

 progressively reduced. The writer regards the gelat- 

 inous covering of these eggs as a protection against 

 loss of fertilizin, and has shown (chap, vii) that after 

 complete removal of jelly sea urchin eggs are much 

 less resistant against loss of fertilizing capacity by 

 repeated washings. Loeb has suggested that loss of 

 vitality would account for the result (1915, p. 283), 

 but, apart from the vagueness of the suggestion, there 

 are other reasons for assigning a more specific cause, 

 which will be discussed later. 



