S. RANZI 311 



lower quantity of material than in the controls remains in solu- 

 tion. Also with this experiment it can be shown that LiCl, by act- 

 ing on the embryos, inhibits demolition while NaSCN makes 

 demolition easier. 



Predisposition and Inhibition to Demolition 

 of Protoplasmic Structures 



The action of animalizing agents which predisposes to demoli- 

 tion and of vegetalizing agents which inhibits demolition has 

 been shown also on some cell structures. Orlandi (1953) showed 

 that Nal, NaSCN, urea, iodosobenzoate, and high pH, disinte- 

 grate the isolated chromosomes, whereas LiCl preserves them. 

 L. Cigada (1954) showed that Nal, NaSCN, methylene blue, and 

 high pH disintegrate the isolated yolk granules whereas LiCl 

 and thiourea preserve them. Brioschi ( 1955 ) working on glyc- 

 erinated muscle fibers showed that while in the presence of 

 vegetalizing substances they regularly contract because of ATP, 

 this property is lost or reduced when animalizing agents are 

 present. 



The demolishing action induced by animalizing agents and the 

 resistance to demolition induced by vegetalizing agents are there- 

 fore phenomena which concern not only embryonic proteins but 

 also structures in the cell. 



The Nature of Denaturation Induced by Animalizing Agents 



Another problem is the nature of the denaturation induced 

 by animalizing agents on these proteins. In the past I have put 

 forward the hypothesis that smaller units could be liberated by 

 the action of animalizing agents. Viscosimetric readings taken 

 this year give an intrinsic viscosity of 0.16 for these subunits 

 (that is, an axial ratio slightly above 11, by admitting a prolate 

 ellipsoid ) . 



From all the above data it seems today that the predisposition 

 to the demolition phenomenon (of which the formation of these 

 subunits represents only one part of the process) is the aspect of 

 greatest importance of embryonic determination. 



