FERTILIZATION' 1 77 



tilization should lead to an acceleration of a process of development, 

 if it were true that the nature of fertiUzation consisted in a positive cataly- 

 sis. I combined fertihzation.by sperm, osmotic fertilization, and the 

 new method of fertihzation in all possible ways in the egg of Stron- 

 ' gylocentrotus without, however, being able to accelerate the process 

 of development ; on the contrary, as a rule, the process of development 

 was markedly retarded. The idea that the spermatozoon carries a 

 positive catalyzer into the egg has, therefore, thus far not received any 

 support. 



A second possibility which was to be considered was that the sper- 

 matozoon removes from the egg somehow a negative catalyzer or a condi- 

 tion whose presence in the egg prevents the development of the latter. If 

 this were the case, we could readily understand why a rise in temperature 

 which accelerates the development in the f ertihzed egg cannot — as far 

 as my present knowledge goes — start the process of development in 

 the unfertilized egg. We can, moreover, well understand why a process 

 of secretion which seems to underhe the membrane formation may be 

 of such great importance for the process of development. Finally, we 

 may be able to understand a fact which I have observed in the eggs of 

 starfish, and which has not yet been mentioned. When the eggs of 

 Asterina or Asierias are allowed to ripen, they will die within a few hours 

 unless they develop either spontaneously or through the influence of 

 sperm or some of the above-mentioned agencies.* The disintegration 

 which leads to the death of the nondeveloping egg is obviously due to 

 an oxidation, since I found that the same eggs when kept in the absence 

 of oxygen will not disintegrate. We know that oxygen is an absolute 

 prerequisite for the development of the fertihzed egg. The fact that 

 oxygen is a poison for the mature but nondeveloping egg shows that 

 altogether different chemical processes must occur in the unfertiUzed, 

 nondeveloping and the developing egg of the starfish. The process of 

 fertihzation seems, therefore, to consist in the elimination or alteration 

 of a chemical condition in the egg, and that this alteration makes the 

 processes of synthesis of nuclein material from the protoplasm possible. 



In my first experiments on artificial parthenogenesis I was inchned 

 to believe that the immediate effect of the methods employed consisted 

 in a modification of the condition of the colloids in the egg. This view 

 is contradicted by my recent experiments. When the process of arti- 

 ficial membrane formation is produced in the egg of a sea urchin, the 

 egg does not show the changes leading to a cell division, e.g. the forma- 

 tion of astrospheres, until after one or two hours. But even this does not 



* Loeb, PJluger's Arckiv, Vol. 93, p. 59, 1902. University of California Publications, 

 Physiology, Vol. 2, p. 147, 1905. 



