S. RANZI 313 



Shaver, 1955) which shows a higher oxydoreduction potential. 

 On the other hand, the analyses carried out directly demonstrate 

 the protein breakdown. In the frog blastoporal dorsal lip, that is, 

 the notochordal rudiment at the time at which it is sensitive to 

 animalizing and vegetalizing agents, Deuchar ( 1955 ) found a 

 higher quantity of free amino acids than in other areas of the 

 embryo. 



The findings of Kavanau (1954) also seem important. He 

 found that the highest quantity of free amino acids in sea urchin 

 embryos occurs exactly during the stage which Biickstrom and 

 Gustafson ( 1953 ) found more sensitive to the action of LiCl. 



Conclusion 



The above indicates that animalization and vegetalization orig- 

 inate from the enlargement or inhibition of the areas in which a 

 process of protein demolition, necessary for new protein synthesis, 

 is acting. The following hypothesis may be formulated: It is pos- 

 sible to represent the unfertilized sea urchin egg with much more 

 reactive protoplasm at the animal pole. Fertilization, by activating 

 certain enzymatic systems according to the conception of Runn- 

 strom ( 1949 ) , activates a higher metabolism in the animal pole. 

 If we bear in mind the fact evidenced by the Stockholm School 

 that several metabolites are animalizing substances, the activation 

 of enzymes and the following formation of metabolites, occurring 

 at the animal pole, seem to lead to the development of the ani- 

 mal pole, while the vegetative pole is stabilized because of failure 

 to form these metabolites. 



Addendum 



A new train of research was performed in this field by the Milan group 

 during the last year (Ranzi et al., 1957). The salting out diagrams of 

 proteins extracted from the sea urchin, Arbacia lixula L., were studied. 



The animalized embryos show proteic fractions precipitating at higher 

 ammonium sulfate concentration than those of the controls, whereas the 

 vegetalized embryos show some fractions precipitating at lower ammonium 

 sulfate concentration. Proteins from embryos animalized by iodosobenzoic 

 acid treatment show salting out diagrams identical to those of the NaSCN 

 animalized embryos. In immunological experiments the two kinds of ani- 

 malized embryos are identical and both show some diflFerences with the 



