450 



SCIENCE 



[N. S. Vol. XXXVin. No. 978 



These observations suggest that the ovarian 

 extract, as well as the secretions of the egg on 

 fertilization contain substances that not only 

 influence permeability, but may reduce the 

 oxidations in the cell. 



Vin. THE THEORY OF INITIATION 



The theory of initiation, as given by Loeb, 

 postulates essentially that initiatory influences 

 place the egg in a condition in which its oxi- 

 dative processes can proceed, or proceed nor- 

 mally. This is accomplished by increasing 

 the permeability of the egg, and in the case of 

 many parthenogenetic agents, as well as in 

 normal fertilization by sperm, the permeabil- 

 ity change may be brought about by lipoid 

 solvents. The fertilization membrane may or 

 may not appear after the use of lipoid sol- 

 vents, and when, as in the case of the starfish 

 egg, it does appear, it may also be made to do 

 so with any other method of increasing the 

 permeability of the plasma film. These facts, 

 many of which have been emphasized by Loeb," 

 E. S. Lillie" and others, by no means prove 

 that the theory of initiation is wrong. Indeed, 

 they are all in harmony with this view if we 

 remember that an hydrophilous fertilization 

 membrane may or may not appear, depending 

 on circumstances, whereas an anhydrophilous 

 one like that of Asterias is certain to appear 

 when, as the result of a permeability change, 

 the egg shrinks away from its enclosing 

 capsule. 



How can increased permeability initiate 

 development ? 



The ovum demonstrably has the necessary 

 mechanism to undergo development of itself. 

 It is a cell with a long metabolic history and 

 before development is initiated its plasma film 

 is relatively impermeable. This may involve 

 the accumulation of " waste " products, and 

 these we may believe to automatically inhibit 

 further metabolic processes. Loeb has shown 

 that these processes are oxidations, and my 

 experiments show that substances can be ex- 

 tracted from the eggs which reduce the rate of 

 development and have a marked efl^ect in de- 



•LiUie, E. S., "The Physiology of Cell Divi- 

 sion," Jour, of Morph., Vol. 22. 



creasing the activity of Arhacia as well as 

 Arenicola larvEe. It does not seem unreason- 

 able to suppose therefore that these materials 

 are active because they reduce oxidations. The 

 mere fact that they also increase cell per- 

 meability and are good initiatory agents is 

 beside the point, for increased permeability 

 in Arenicola larvas is also associated with 

 acceleration of movement. 



One may extend the theory of initiation 

 and assume that all agencies that initiate de- 

 velopment do so because through increased 

 permeability of the plasma film the egg is 

 enabled to loose substances antagonistic to 

 oxidation. By freeing itself of these inhib- 

 itors, a chemical equilibrium is disturbed, and 

 oxidation, and with it development, is free t^ 

 go on. 



In this way we can explain why a mature 

 starfish egg, if unfertilized, may oxidize itself 

 to death, for we may suppose that its per- 

 meability has been sufiiciently increased by 

 maturation to accelerate oxidation, but not 

 enough to initiate development proper. We 

 can also bring all parthenogenetic methods 

 whatsoever, as well as normal fertilization, 

 under a common point of view, for the in- 

 creased permeability, no matter whether pro- 

 duced by electricity, heat, cold, mechanical 

 shock, specific chemical alteration of the mem- 

 brane, lipoid solvents, or pricking, is all that 

 is necessary to enable the egg to free itseK 

 from its accumulated inhibitors. Why the 

 egg should develop after treatment with hyper- 

 tonic solutions is also clear, for if in such 

 media the plasma film is permeable to the 

 inhibitors, loss of water by the egg would, 

 directly or indirectly, accelerate the loss of 

 antagonists. That these are lost in hyper- 

 tonic sea water is shown by special experi- 

 ments. 



In conclusion, I must thank my colleague, 

 Dr. W. E. Garrey, who kindly allowed me to 

 demonstrate to him various steps in the in- 

 vestigation, and to whom I am indebted for a 

 number of valuable suggestions and criticisms. 

 Otto Glaser 



Woods Hole, Mass., 

 August 4, 1913 



